Semiconductor device

ABSTRACT

Provided is a semiconductor device including: a semiconductor substrate having upper and lower surfaces and throughout which a first-conductivity-type bulk donor is distributed; a first-conductivity-type high concentration region including a center position in a depth direction of the substrate and having a donor concentration higher than a doping concentration of the donors; and an upper surface side oxygen reduction region provided in contact with the upper surface inside the substrate and in which an oxygen chemical concentration decreases as approaching the upper surface. The oxygen chemical concentration distribution may have a maximum value region where the oxygen chemical concentration is 50% or more of the maximum value, a first peak of an impurity chemical concentration may be arranged in an end of the high concentration region in the depth direction, and the peak may be arranged on the upper surface side with respect to or in the maximum value region.

The contents of the following Japanese and PCT patent applications areincorporated herein by reference:

-   No. 2020-025326 filed in JP on Feb. 18, 2020, and-   No. PCT/JP2021/006016 filed in WO on Feb. 17, 2021.

BACKGROUND 1. Technical Field

The present invention relates to a semiconductor device.

2. Related Art

Conventionally, it is known that a semiconductor wafer is radiated withprotons to perform a thermal process so as to “generate hydrogen induceddonors from crystal defects formed by proton radiation and introducedproton” (see, for example, paragraph 0061 of Patent Document 1).

-   Patent Document 1: Japanese Patent Application Publication No.    2013-153183.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a sectional view showing an example of asemiconductor device 100.

FIG. 2 illustrates a distribution example of an oxygen chemicalconcentration C_(OX), an impurity chemical concentration C_(I), ahydrogen chemical concentration C_(H), and a VOH defect concentrationN_(VOH) in a depth direction at a position indicated by line A-A in FIG.1.

FIG. 3 illustrates another distribution example of the oxygen chemicalconcentration C_(OX), the impurity chemical concentration C_(I), thehydrogen chemical concentration C_(H), and the VOH defect concentrationN_(VOH) in the depth direction at the position indicated by the line A-Ain FIG. 1.

FIG. 4 illustrates a diagram showing an example of a variation in oxygenchemical concentration distribution of an MCZ substrate before and afteroxygen annealing.

FIG. 5 illustrates a diagram showing an example of a variation in oxygenchemical concentration distribution of an FZ substrate before and afteroxygen annealing.

FIG. 6 illustrates a diagram showing a distribution example of arecombination center concentration N_(r) and an oxygen chemicalconcentration C_(OX).

FIG. 7 illustrates a diagram describing a position of a third peak 403.

FIG. 8 illustrates an example of a top view of the semiconductor device100.

FIG. 9 illustrates an enlarged view of a region A in FIG. 8.

FIG. 10 illustrates a diagram showing an example of a cross section b-bin FIG. 9.

FIG. 11 illustrates a diagram showing an example of a cross section c-cin FIG. 8.

FIG. 12 illustrates distribution examples of a carrier concentrationN_(c), a phosphorous chemical concentration C_(P), a VOH defectconcentration N_(VOH), and an impurity chemical concentration C_(I)along the d-d line illustrated in FIG. 11.

FIG. 13A illustrates a diagram showing another example of the crosssection c-c in FIG. 8.

FIG. 13B illustrates a diagram showing another example of the crosssection c-c in FIG. 8.

FIG. 13C illustrates a diagram showing another example of the crosssection c-c in FIG. 8.

FIG. 14 illustrates a diagram showing another example of the crosssection c-c in FIG. 8.

FIG. 15 illustrates a diagram showing another example of the crosssection c-c in FIG. 8.

FIG. 16 illustrates a diagram showing another example of the crosssection c-c in FIG. 8.

FIG. 17 illustrates a diagram showing another example of the crosssection c-c in FIG. 8.

FIG. 18A illustrates a diagram showing another example of the crosssection c-c in FIG. 8.

FIG. 18B illustrates a diagram showing another example of the crosssection c-c in FIG. 8.

FIG. 18C illustrates a diagram showing another example of the crosssection c-c in FIG. 8.

FIG. 19 illustrates a diagram showing another example of the crosssection c-c in FIG. 8.

FIG. 20 illustrates a diagram showing another example of the crosssection c-c in FIG. 8.

FIG. 21A illustrates a diagram showing another example of the crosssection c-c in FIG. 8.

FIG. 21B illustrates a diagram showing another example of the crosssection c-c in FIG. 8.

FIG. 22 illustrates a diagram showing an example of a method for forminga high concentration region 460 described in FIG. 20.

FIG. 23 illustrates a diagram showing an example of a method for formingthe high concentration region 460 described in FIG. 21A.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, the invention will be described through embodiments of theinvention, but the following embodiments do not limit the inventionaccording to claims. In addition, not all of the combinations offeatures described in the embodiments are essential to the solving meansof the invention.

As used herein, one side in a direction parallel to a depth direction ofa semiconductor substrate is referred to as “upper” and the other sideis referred to as “lower”. One surface of two principal surfaces of asubstrate, a layer or other member is referred to as an upper surface,and the other surface is referred to as a lower surface. “Upper” and“lower” directions are not limited to a direction of gravity, or adirection in which a semiconductor device is mounted.

In the present specification, technical matters may be described usingorthogonal coordinate axes of an X axis, a Y axis, and a Z axis. Theorthogonal coordinate axes merely specify relative positions ofcomponents, and do not limit a specific direction. For example, the Zaxis is not limited to indicate the height direction with respect to theground. Note that a +Z axis direction and a −Z axis direction aredirections opposite to each other. When the Z axis direction isdescribed without describing the signs, it means that the direction isparallel to the +Z axis and the −Z axis.

In the present specification, orthogonal axes parallel to the uppersurface and the lower surface of the semiconductor substrate arereferred to as the X axis and the Y axis. Further, an axis perpendicularto the upper surface and the lower surface of the semiconductorsubstrate is referred to as the Z axis. In the present specification,the direction of the Z axis may be referred to as the depth direction.Further, in the present specification, a direction parallel to the uppersurface and the lower surface of the semiconductor substrate may bereferred to as a horizontal direction, including an X axis direction anda Y axis direction. In the case of referring to an upper surface side ofthe semiconductor substrate in the present specification, the uppersurface side indicates a region from the center to the upper surface inthe depth direction of the semiconductor substrate. In the case ofreferring to a lower surface side of the semiconductor substrate, thelower surface side indicates a region from the center to the lowersurface in the depth direction of the semiconductor substrate.

In the present specification, a case where a term such as “same” or“equal” is mentioned may include a case where an error due to avariation in manufacturing or the like is included. The error is, forexample, within 10%.

In the present specification, a conductivity type of doping region wheredoping has been carried out with an impurity is described as a P type oran N type. In the present specification, the impurity may particularlymean either a donor of the N type or an acceptor of the P type, and maybe described as a dopant. In the present specification, doping meansintroducing the donor or the acceptor into the semiconductor substrateand turning it into a semiconductor presenting a conductivity type ofthe N type, or a semiconductor presenting conductivity type of the Ptype.

In the present specification, a doping concentration means aconcentration of the donor or a concentration of the acceptor in athermal equilibrium state. In the present specification, a net dopingconcentration means a net concentration obtained by adding the donorconcentration set as a positive ion concentration to the acceptorconcentration set as a negative ion concentration, taking into accountof polarities of charges. As an example, when the donor concentration isN_(D) and the acceptor concentration is N_(A), the net net dopingconcentration at any position is given as N_(D)-N_(A).

The donor has a function of supplying electrons to a semiconductor. Theacceptor has a function of receiving electrons from the semiconductor.The donor and the acceptor are not limited to the impurities themselves.For example, a VOH defect which is a combination of a vacancy (V),oxygen (O), and hydrogen (H) existing in the semiconductor functions asthe donor that supplies electrons.

In the present specification, a description of a P+ type or an N+ typemeans a higher doping concentration than that of the P type or the Ntype, and a description of a P− type or an N− type means a lower dopingconcentration than that of the P type or the N type. Further, in thespecification, a description of a P++ type or an N++ type means a higherdoping concentration than that of the P+ type or the N+ type.

A chemical concentration in the present specification indicates anatomic density of an impurity measured regardless of an electricalactivation state. The chemical concentration (atomic density) can bemeasured by, for example, secondary ion mass spectrometry (SIMS). Thenet doping concentration described above can be measured byvoltage-capacitance profiling (CV profiling). Further, a carrierconcentration measured by spreading resistance profiling (SRP method)may be set as the net doping concentration. The carrier concentrationmeasured by the CV profiling or the SRP method may be a value in athermal equilibrium state. Further, in a region of the N type, the donorconcentration is sufficiently higher than the acceptor concentration,and thus the carrier concentration of the region may be set as the donorconcentration. Similarly, in a region of the P type, the carrierconcentration of the region may be set as the acceptor concentration.

Further, when a concentration distribution of the donor, acceptor, ornet doping has a peak in a region, a value of the peak may be set as theconcentration of the donor, acceptor, or net doping in the region. In acase where the concentration of the donor, acceptor or net doping issubstantially uniform in a region, or the like, an average value of theconcentration of the donor, acceptor or net doping in the region may beset as the concentration of the donor, acceptor or net doping.

The carrier concentration measured by the SRP method may be lower thanthe concentration of the donor or the acceptor. In a range where acurrent flows when a spreading resistance is measured, carrier mobilityof the semiconductor substrate may be lower than a value in acrystalline state. The reduction in carrier mobility occurs whencarriers are scattered due to disorder (disorder) of a crystal structuredue to a lattice defect or the like.

The concentration of the donor or the acceptor calculated from thecarrier concentration measured by the CV profiling or the SRP method maybe lower than a chemical concentration of an element indicating thedonor or the acceptor. As an example, in a silicon semiconductor, adonor concentration of phosphorous or arsenic serving as a donor, or anacceptor concentration of boron serving as an acceptor is approximately99% of chemical concentrations of these. On the other hand, in thesilicon semiconductor, a donor concentration of hydrogen serving as adonor is approximately 0.1% to 10% of a chemical concentration ofhydrogen.

FIG. 1 illustrates a sectional view showing an example of asemiconductor device 100. The semiconductor device 100 includes asemiconductor substrate 10. The semiconductor substrate 10 is asubstrate that is formed of a semiconductor material. As an example, thesemiconductor substrate 10 is a silicon substrate.

At least one of a transistor element such as an insulated gate bipolartransistor (IGBT) and a diode element such as a freewheeling diode (FWD)is formed on the semiconductor substrate 10. In FIG. 1, each electrodeof the transistor device and the diode device and each region providedinside the semiconductor substrate 10, of the transistor element and thediode element are omitted.

In the semiconductor substrate 10 of the this example, bulk donors of anN type are distributed throughout. The bulk donor is a dopant donorsubstantially uniformly contained in an ingot during the manufacture ofthe ingot from which the semiconductor substrate 10 is made. The bulkdonor of the this example is an element other than hydrogen. The bulkdonor dopant is, for example, an element of Group V or Group VI, and is,for example, but not limited to, phosphorous, antimony, arsenic,selenium, or sulfur. The bulk donor of the this example is phosphorous.The bulk donor is also contained in the P type region. The semiconductorsubstrate 10 may be a wafer cut out from a semiconductor ingot, or maybe a chip obtained by singulating the wafer. The semiconductor ingot maybe manufactured by any one of a Czochralski method (CZ method), amagnetic field applied Czochralski method (MCZ method), and a float zonemethod (FZ method).

An oxygen chemical concentration contained in the substrate manufacturedby the MCZ method is, for example, 1×10¹⁷ to 7×10¹⁷ atoms/cm³. Theoxygen chemical concentration contained in the substrate manufactured bythe FZ method is, for example, 1×10¹⁵ to 5×10¹⁶ atoms/cm³. The bulkdonor concentration may use a chemical concentration of bulk donorsdistributed throughout the semiconductor substrate 10, and may be avalue between 90% and 100% of the chemical concentration. In thesemiconductor substrate doped with dopants of groups V and VI such asphosphorous, the bulk donor concentration may be 1×10¹¹/cm³ or more and3×10¹³/cm³ or less. The bulk donor concentration of the semiconductorsubstrate doped with the dopants of groups V and VI is preferably1×10¹²/cm³ or more and 1×10¹³/cm³ or less. As the semiconductorsubstrate 10, a non-doped substrate substantially not containing a bulkdopant such as phosphorous may be used. In that case, the bulk donorconcentration (N_(B0)) of the non-doped substrate is, for example,1×10¹⁰/cm³ or more and 5×10¹²/cm³ or less. The bulk donor concentration(N_(B0)) of the non-doped substrate is preferably 1×10¹¹/cm³ or more.The bulk donor concentration (N_(B0)) of the non-doped substrate ispreferably 5×10¹²/cm³ or less.

The semiconductor substrate 10 has an upper surface 21 and a lowersurface 23. The upper surface 21 and the lower surface 23 are twoprincipal surfaces of the semiconductor substrate 10. In thespecification, orthogonal axes in the plane that is parallel to theupper surface 21 and the lower surface 23 is referred to as an x axisand a y axis, and the perpendicular axis to the upper surface 21 and thelower surface 23 is referred to as a z axis.

A charged particle beam is implanted from the lower surface 23 into thesemiconductor substrate 10 at a predetermined depth position Z1. Theprincipal surface of the semiconductor substrate 10 into which thecharged particle beam is implanted may not be limited to the lowersurface 23 and may be the upper surface 21. In the presentspecification, the distance from the upper surface 21 in the Z axisdirection may be referred to as a depth position. In the presentspecification, the center position in the depth direction of thesemiconductor substrate 10 is defined as a depth position Zc. The depthposition Z1 is a position where the distance from the upper surface 21in the Z axis direction is Z1. The depth position Z1 is arranged on theupper surface 21 side of the semiconductor substrate 10 (a regionbetween the depth position Zc and the upper surface 21). Implantation ofthe charged particle beam into the depth position Z1 means that anaverage distance (also referred to as a range) of charged particlespassing through the inside of the semiconductor substrate 10 is Z1. Thecharged particles are accelerated by acceleration energy correspondingto the predetermined depth position Z1 and introduced into thesemiconductor substrate 10.

A region where the charged particles have passed through the inside ofthe semiconductor substrate 10 is defined as a pass-through region 106.In the example of FIG. 1, a region from the lower surface 23 of thesemiconductor substrate 10 to the depth position Z1 is the pass-throughregion 106. The charged particles are particles capable of forminglattice defects in the pass-through region 106. The charged particlesare, for example, hydrogen ions, helium ions, or electrons. The chargedparticles may be implanted into the entire surface of the semiconductorsubstrate 10 in the XY plane, or may be implanted into only a partialregion.

The semiconductor substrate 10 has a first peak 401 of the chargedparticle concentration at the depth position Z1. In the this example,the charged particles are hydrogen. That is, the semiconductor substrate10 of the this example has the first peak 401 in the depth direction ofthe hydrogen chemical concentration at the depth position Z1. The firstpeak 401 may be a peak in the helium chemical concentrationdistribution.

In the pass-through region 106 through which the charged particles havepassed in the semiconductor substrate 10, lattice defects mainlycomposed of vacancies such as monatomic vacancies (V) and diatomicvacancies (VV) are formed by the charged particles passing therethrough.Atoms adjacent to the vacancies have dangling bonds. Lattice defectsalso include interstitial atoms, dislocations, and the like, and mayinclude donors and acceptors in a broad sense. However, in the presentspecification, lattice defects mainly composed of vacancies may bereferred to as vacancy-type lattice defects, vacancy-type defects, orsimply lattice defects. In addition, since many lattice defects areformed by implantation of charged particles into the semiconductorsubstrate 10, the crystallinity of the semiconductor substrate 10 may bestrongly disturbed. In the present specification, this disturbance ofcrystallinity may be referred to as disorder.

In addition, oxygen is contained in the entire semiconductor substrate10. The oxygen is introduced intentionally or unintentionally duringmanufacturing a semiconductor ingot. Hydrogen is contained in at least apartial region of the pass-through region 106. The hydrogen may beintentionally implanted into the semiconductor substrate 10.

In the this example, hydrogen ions are implanted into a depth positionZ2 from the lower surface 23. The hydrogen ions of the this example areprotons. The principal surface of the semiconductor substrate 10 intowhich hydrogen ions are implanted may not be limited to the lowersurface 23 and may be the upper surface 21. The semiconductor substrate10 of the this example has a second peak 402 of hydrogen chemicalconcentration at the depth position Z2. In FIG. 1, the first peak 401and the second peak 402 are schematically indicated by broken lines. Thedepth position Z2 may be included in the pass-through region 106. Thedepth position Z2 of the this example is arranged on the lower surface23 side of the semiconductor substrate 10 (a region between the depthposition Zc and the lower surface 23). Note that hydrogen implanted atthe depth position Z1 may be diffused into the pass-through region 106,or hydrogen may be introduced into the pass-through region 106 byanother method. In these cases, hydrogen ions may not be implanted intothe depth position Z2.

After the pass-through region 106 is formed in the semiconductorsubstrate 10 and hydrogen ions are implanted into the semiconductorsubstrate 10, hydrogen (H), vacancies (V), and oxygen (O) are combinedinside the semiconductor substrate 10, and VOH defects are formed. Inaddition, heat treatment (sometimes referred to as annealing in thepresent specification) of the semiconductor substrate 10 diffuseshydrogen to promote formation of VOH defects. In addition, sincehydrogen can be combined to the vacancies by heat treatment afterforming the pass-through region 106, it is possible to suppress releaseof hydrogen to the outside of the semiconductor substrate 10.

The VOH defect functions as a donor that supplies electrons. In thepresent specification, VOH defects may be referred to simply as hydrogendonors. In the semiconductor substrate 10 of the this example, ahydrogen donor is formed in the pass-through region 106. The dopingconcentration of the hydrogen donor at each position is lower than thechemical concentration of hydrogen at each position. Regarding thechemical concentration of hydrogen, the ratio of the chemicalconcentration of hydrogen to the doping concentration of hydrogen donors(VOH defects) may be a value between 0.1% and 30% (that is, 0.001 ormore and 0.3 or less). In the this example, the ratio of the chemicalconcentration of hydrogen to the doping concentration of hydrogen donors(VOH defects) is 1% to 5%. Note that, unless otherwise specified, in thepresent specification, VOH defects having a distribution similar to thechemical concentration distribution of hydrogen and VOH defects similarto the distribution of vacancy defects in the pass-through region 106are also referred to as hydrogen donors or hydrogen as donors.

By forming a hydrogen donor in the pass-through region 106 of thesemiconductor substrate 10, the donor concentration in the pass-throughregion 106 can be made higher than the doping concentration of the bulkdonor (also referred to simply as bulk donor concentration) of the bulkdonor. Normally, it is necessary to prepare the semiconductor substrate10 having a predetermined bulk donor concentration in accordance withcharacteristics of an element to be formed on the semiconductorsubstrate 10, particularly a rated voltage or a breakdown voltage. Onthe other hand, according to the semiconductor device 100 illustrated inFIG. 1, the donor concentration of the semiconductor substrate 10 can beadjusted by controlling the dosing amount of charged particles.Therefore, the semiconductor device 100 can be manufactured using asemiconductor substrate having a bulk donor concentration that does notcorrespond to the characteristics and the like of the element. Thevariation in the bulk donor concentration during manufacturing thesemiconductor substrate 10 is relatively large, but the dosing amount ofthe charged particles can be controlled with relatively high precision.Therefore, the concentration of lattice defects generated by implantedcharged particles can also be controlled with high precision, and thedonor concentration in the pass-through region can be controlled withhigh precision.

The depth position Z1 may be arranged in a range of half or less of thethickness of the semiconductor substrate 10 with respect to the uppersurface 21, or may be arranged in a range of ¼ or less of the thicknessof the semiconductor substrate 10. The depth position Z2 may be arrangedin a range of half or less of the thickness of the semiconductorsubstrate 10 with respect to the lower surface 23, or may be arranged ina range of ¼ or less of the thickness of the semiconductor substrate 10.However, the depth position Z1 and the depth position Z2 are not limitedto these ranges.

The semiconductor substrate 10 has an upper surface side oxygenreduction region 450. The upper surface side oxygen reduction region 450is a region inside the semiconductor substrate 10 and is a region incontact with the upper surface 21 of the semiconductor substrate 10. Theupper surface side oxygen reduction region 450 is a region where theoxygen chemical concentration decreases as the depth position approachesthe upper surface 21. The upper surface side oxygen reduction region 450may be a region where the oxygen chemical concentration decreases over alength of 3% or more of the substrate thickness of the semiconductorsubstrate 10, a region where the oxygen chemical concentration decreasesover a length of 5% or more of the substrate thickness, or a regionwhere the oxygen chemical concentration decreases over a length of 10%or more of the substrate thickness. The substrate thickness refers tothe thickness of the semiconductor substrate 10 in the depth direction.

In a semiconductor ingot or a wafer cut out from the ingot, oxygenhaving a approximately uniform concentration is contained in the entiresubstrate. However, the variation in oxygen chemical concentrationbetween the substrates is relatively large. When the oxygen chemicalconcentration varies, the concentration of VOH defects formed byimplanted hydrogen tends to vary.

In the this example, the semiconductor substrate 10 is annealed at apredetermined annealing temperature and a predetermined annealing time.The semiconductor substrate 10 may be annealed in a state of a wafer cutout from an ingot, or may be annealed in a state of a chip cut out froma wafer. The annealing is preferably performed before the implantationof the charged particle beam. In the present specification, theannealing before the implantation of the charged particle beam may bereferred to as oxygen annealing.

At the time of oxygen annealing, the surface of the semiconductorsubstrate 10 may be exposed to an oxygen-containing atmosphere or anoxide film may be formed. The oxygen annealing time is long enough tointroduce oxygen having a concentration of a solid solubility limitcorresponding to the oxygen annealing temperature into the substrate.The oxygen annealing time may be 1 hour or more, 2 hours or more, or 10hours or more. The solid solubility limit of oxygen refers to a limitconcentration of oxygen that can be dissolved in the substrate, andvaries depending on the oxygen annealing temperature. The oxygenannealing temperature is, for example, 1000° C. or higher, but is notlimited thereto. The oxygen annealing temperature may be set so that thesolid solubility limit of oxygen is sufficiently higher than the oxygenchemical concentration of the semiconductor substrate 10 before oxygenannealing.

By performing oxygen annealing with an oxygen annealing time equal to orlonger than a certain value, oxygen having a chemical concentrationapproximately matching the solid solubility limit is introduced into thesemiconductor substrate 10. Therefore, the oxygen chemical concentrationof the semiconductor substrate 10 can be controlled by managing theoxygen annealing temperature so as to have a solid solubility limitcorresponding to a desired oxygen chemical concentration. In addition,since the oxygen annealing temperature can be managed relatively easily,variation in oxygen chemical concentration between the substrates canalso be reduced.

In the process of taking out the semiconductor substrate 10 from theoxygen atmosphere and returning the temperature from the oxygenannealing temperature to room temperature, oxygen in the vicinity of thesurface of the semiconductor substrate 10 diffuses out of the substrate(referred to as outward diffusion in the present specification). Theoutward diffusion is more likely to occur as it is closer to the surfaceof the semiconductor substrate 10. Therefore, the upper surface sideoxygen reduction region 450 is formed in the semiconductor substrate 10.Note that a lower surface side oxygen reduction region is also formed ina region in contact with the lower surface 23 of the semiconductorsubstrate 10. However, in a case where the lower surface 23 side of thesemiconductor substrate 10 is ground, the lower surface side oxygenreduction region may not remain.

Such processing can reduce variations in oxygen chemical concentrationin the semiconductor substrate 10. Therefore, the concentration of VOHdefects can be easily controlled, and the donor concentration of thesemiconductor substrate 10 can be easily controlled.

FIG. 2 illustrates a distribution example of an oxygen chemicalconcentration C_(OX), an impurity chemical concentration C_(I), ahydrogen chemical concentration C_(H), a VOH defect concentrationN_(VOH), and a net doping concentration N_(D) in the depth direction atthe position indicated by the line A-A in FIG. 1. FIG. 2 illustrateseach distribution after oxygen annealing and hydrogen annealing afterhydrogen implantation.

In FIG. 2, the horizontal axis represents the depth position from theupper surface 21, and the vertical axis represents each concentrationper unit volume on a logarithmic axis. The chemical concentration inFIG. 2 is measured by, for example, a SIMS method. In FIG. 2, a bulkdonor concentration N_(B) is indicated by a broken line. The bulk donorconcentration N_(B) may be uniform throughout the semiconductorsubstrate 10. The semiconductor substrate 10 of the this example is anMCZ substrate as an example.

The distribution of the oxygen chemical concentration C_(OX) has theupper surface side oxygen reduction region 450. As described above,oxygen in the vicinity of the upper surface 21 is diffused outward byperforming oxygen annealing. In the this example, the lower surface 23side of the semiconductor substrate 10 is ground after oxygen annealing.Therefore, the lower surface side oxygen reduction region is notprovided on the lower surface 23 of the semiconductor substrate 10.

In the upper surface side oxygen reduction region 450, the reductionrate of the oxygen chemical concentration with respect to the unitdistance in the depth direction may increase toward the upper surface21. That is, the oxygen chemical concentration may decrease more steeplytoward the upper surface 21.

The distribution of the oxygen chemical concentrations C_(OX) has amaximum value region 452. The maximum value region 452 is a regionincluding a position where the oxygen chemical concentration C_(OX)becomes a maximum value C_(OX_max) in the depth direction and is aregion where the oxygen chemical concentration C_(OX) is equal to ormore than a predetermined boundary concentration C_(b). The boundaryconcentration C_(b) may be 50%, 70%, 80% or more, 90% or more, or 100%of the maximum value C_(OX_max). The upper surface side oxygen reductionregion 450 of the this example is arranged between the maximum valueregion 452 and the upper surface 21. A depth position of a boundarybetween the upper surface side oxygen reduction region 450 and themaximum value region 452 is defined as Zb. The maximum value region 452of the this example is provided from the depth position Zb to the lowersurface 23.

The maximum value C_(OX_max) may be 3×10¹⁵ atoms/cm³ or more and 2×10¹⁸atoms/cm³ or less. The maximum value C_(OX_max) may be 1×10¹⁶ atoms/cm³or more, or 1×10¹⁷ atoms/cm³ or more. The maximum value C_(OX_max) maybe 1×10¹⁸ atoms/cm³ or less, or 1×10¹⁷ atoms/cm³ or less.

The impurity chemical concentration C_(I) has a first peak 401 at thedepth position Z1. In the this example, the impurity is hydrogen. Thedistribution of the impurity chemical concentration C_(I) has an uppertail 411 in which the impurity chemical concentration C_(I) decreasesfrom the first peak 401 toward the upper surface 21, and a lower tail421 in which the impurity chemical concentration C_(I) decreases fromthe first peak 401 toward the lower surface 23. As described in FIG. 1,impurities (hydrogen in the this example) are implanted into the depthposition Z1 from the lower surface 23. Therefore, the impurity chemicalconcentration C_(I) of the upper tail 411 may decrease more steeply thanthat of the lower tail 421. The lower tail 421 may be provided from thefirst peak 401 to the lower surface 23. The impurity chemicalconcentration C_(I) may be a chemical concentration of hydrogenimplanted into the depth position Z1 from the lower surface 23 of thesemiconductor substrate 10. The first peak 401 may be arranged in theupper surface side oxygen reduction region 450. The depth position Z1 ofthe first peak 401 may be arranged closer to the upper surface 21 thanthe depth position Zc. The depth position Z1 of the first peak 401 maybe arranged closer to the upper surface 21 than the depth positionZ_(b).

A hydrogen chemical concentration C_(H) of the this example has a secondpeak 402 arranged at the depth position Z2 between the first peak 401and the lower surface 23. The second peak 402 of the this example isarranged in the maximum value region 452. The value of the chemicalconcentration of the second peak 402 may be larger than the value of thechemical concentration of the first peak 401. This facilitates thediffusion of hydrogen into the pass-through region 106. The value of thesecond peak 402 may be 2 times or more, 5 times or more, 10 times ormore, or 100 times or more of the value of the first peak 401.

The distribution of the hydrogen chemical concentration C_(H) has anupper tail 412 in which the hydrogen chemical concentration C_(H)decreases from the second peak 402 toward the upper surface 21, and alower tail 422 in which the hydrogen chemical concentration C_(H)decreases from the second peak 402 toward the lower surface 23. Asdescribed in FIG. 1, hydrogen ions are implanted from the lower surface23 to the depth position Z2. Therefore, the hydrogen chemicalconcentration C_(H) of the upper tail 412 may decrease more steeply thanthat of the lower tail 422. However, since hydrogen diffuses from thesecond peak 402 toward the first peak 401 by heat-treating thesemiconductor substrate 10, the upper tail 412 may have a portiongentler than the lower tail 422. At each position between the first peak401 and the second peak 402, hydrogen having a chemical concentration of10 times or more of the bulk donor concentration N_(B) may exist,hydrogen having a chemical concentration of 100 times or more of thebulk donor concentration N_(B) may exist, or hydrogen having a chemicalconcentration of 200 times or more of the bulk donor concentration N_(B)may exist.

The distribution of the VOH defect concentration N_(VOH) of the thisexample has the third peak 403 at the depth position Z1. At the depthposition Z1, many vacancy defects are formed by the implantation of thecharged particle beam. Therefore, many VOH defects are likely to beformed at the depth position Z1. The distribution of the VOH defectconcentration N_(VOH) of the this example has a fourth peak 404 at thedepth position Z2. Many vacancy defects due to the implantation ofhydrogen ions are formed at the depth position Z2. Therefore, many VOHdefects are likely to be formed at the depth position Z2.

The distribution of the VOH defect concentration N_(VOH) has an uppertail 413 in which the VOH defect concentration N_(VOH) decreases fromthe third peak 403 toward the upper surface 21 and a lower tail 423 inwhich the VOH defect concentration N_(VOH) decreases from the third peak403 toward the lower surface 23. The VOH defect concentration N_(VOH) ofthe upper tail 413 may decrease more steeply than that of the lower tail423.

The distribution of the VOH defect concentration N_(VOH) has an uppertail 414 in which the VOH defect concentration N_(VOH) decreases fromthe fourth peak 404 toward the upper surface 21 and a lower tail 424 inwhich the VOH defect concentration N_(VOH) decreases from the fourthpeak 404 toward the lower surface 23. The VOH defect concentrationN_(VOH) of the upper tail 414 may decrease more steeply than that of thelower tail 424.

The net doping concentration N_(D) of the this example has aconcentration obtained by adding the bulk donor concentration N_(B) andthe VOH defect concentration N_(VOH). Since the bulk donor concentrationN_(B) is approximately constant throughout the semiconductor substrate10, the shape of the distribution of the net doping concentration N_(D)is similar to the shape of the distribution of the VOH defectconcentration N_(VOH).

The distribution of the net doping concentration N_(D) of the thisexample has a fifth peak 425 at the depth position Z1. In addition, thedistribution of the net doping concentration N_(D) of the this examplehas a sixth peak 426 at the depth position Z2. The distribution of thenet doping concentration N_(D) has an upper tail 435 in which the netdoping concentration N_(D) decreases from the fifth peak 425 toward theupper surface 21 and a lower tail 445 in which the net dopingconcentration N_(D) decreases from the fifth peak 425 toward the lowersurface 23. The net doping concentration N_(D) of the upper tail 435 maydecrease more steeply than that of the lower tail 445.

The distribution of the net doping concentration N_(D) has an upper tail436 in which the net doping concentration N_(D) decreases from the sixthpeak 426 toward the upper surface 21 and a lower tail 446 in which thenet doping concentration N_(D) decreases from the sixth peak 426 towardthe lower surface 23. The net doping concentration N_(D) of the uppertail 436 may decrease more steeply than that of the lower tail 446.

Note that the positions of the vertexes of the first peak 401, the thirdpeak 403, and the fifth peak 425 may not strictly coincide with eachother. Similarly, the positions of the vertexes of the second peak 402,the fourth peak 404, and the sixth peak 426 may not strictly coincidewith each other. If the vertex of the other peak is arranged within thefull width at half maximum of one peak, the two peaks may be provided atthe same position.

Since VOH defects are formed in the pass-through region 106, the donorconcentration in the pass-through region 106 is higher than the bulkdonor concentration N_(B). In the present specification, a regioncontaining VOH defects and having a donor concentration higher than thebulk donor concentration N_(B) is referred to as a high concentrationregion 460. The high concentration region 460 includes the depthposition Zc of the semiconductor substrate 10 and is provided over apredetermined length in the depth direction. The length of the highconcentration region 460 in the depth direction may be 50% or more, 60%or more, 70% or more, 80% or more, or 90% or more of the substratethickness. The high concentration region 460 of the this example isprovided from the first peak 401 to the lower surface 23.

In addition, the high concentration region 460 may also be providedabove the first peak 401. The first peak 401 has a predeterminedhalf-value width in the depth direction. Therefore, vacancy defects arealso formed above the first peak 401, and the high concentration region460 is formed. However, the high concentration region 460 above thefirst peak 401 has a smaller width in the depth direction than the highconcentration region 460 below the first peak 401.

The high concentration region 460 may be a region where the VOH defectconcentration N_(VOH) is higher than the bulk donor concentration N_(B).As a result, even in a case where the bulk donor concentration N_(B)varies, the variation in donor concentration can be suppressed by theVOH defect concentration N_(VOH) that can be controlled with highprecision. The VOH defect concentration N_(VOH) may be 2 times or more,5 times or more, or 10 times or more of the bulk donor concentrationN_(B).

As illustrated in FIG. 2, the first peak 401 is arranged at an endportion of the high concentration region 460 on the upper surface 21side. The first peak 401 may be arranged in the maximum value region 452or on the upper surface 21 side with respect to the maximum value region452. The first peak 401 of the this example is arranged in the uppersurface side oxygen reduction region 450. As a result, the highconcentration region 460 can be formed in a wider range in the depthdirection. Therefore, the donor concentration of the semiconductorsubstrate 10 can be controlled with high precision in a wider range.

The first peak 401 may be arranged in a region where the oxygen chemicalconcentration C_(OX) is 10% or more, 30% or more, 50% or more, 70% ormore, or 90% or more of the maximum value C_(OX_max). If the oxygenchemical concentration C_(OX) is small, the variation of the oxygenchemical concentration C_(OX) with respect to the positional deviationin the depth direction increases. By arranging the first peak 401 in theregion where the oxygen chemical concentration C_(OX) is equal to ormore than a predetermined value, it is possible to suppress thevariation in the size of the third peak 403 in a case where the depthposition of the first peak 401 is shifted. Therefore, variations incharacteristics of the semiconductor device 100 can be suppressed.

FIG. 3 illustrates another distribution example in the depth directionof the oxygen chemical concentration C_(OX), the impurity chemicalconcentration C_(I), the hydrogen chemical concentration C_(H), the VOHdefect concentration N_(VOH), and the net doping concentration N_(D) atthe position indicated by the line A-A in FIG. 1. FIG. 3 illustrateseach distribution after the heat treatment. In the this example, theoxygen chemical concentration C_(OX) is different from that in theexample of FIG. 2. The other concentration distributions are similar tothose in the example of FIG. 2. The semiconductor substrate 10 of thethis example is, for example, an FZ substrate.

The oxygen chemical concentration C_(OX) of the this example has anoxygen concentration peak 405 indicating the local maximum value C₀ at adepth position Z_(p). The range of the local maximum value C_(OX_max)may be similar to the range of the maximum value C_(OX_max) in FIG. 2.The distribution of the oxygen chemical concentration C_(OX) of the thisexample has a lower surface side oxygen reduction region 454 in additionto the maximum value region 452 and the upper surface side oxygenreduction region 450 illustrated in FIG. 2. The lower surface sideoxygen reduction region 454 is a region which is in contact with thelower surface 23 and in which the oxygen chemical concentration C_(OX)decreases toward the lower surface 23. The maximum value region 452 isarranged between the upper surface side oxygen reduction region 450 andthe lower surface side oxygen reduction region 454.

The lower surface side oxygen reduction region 454 may be a region wherethe oxygen chemical concentration C_(OX) gradually decreases as comparedwith the upper surface side oxygen reduction region 450. The lowersurface side oxygen reduction region 454 may be longer than the uppersurface side oxygen reduction region 450 in the depth direction. As aresult, the variation of the oxygen chemical concentration C_(OX) in thesemiconductor substrate 10 can be made relatively small as compared withthe case where the upper surface side oxygen reduction region 450 islong. The length of the lower surface side oxygen reduction region 454in the depth direction may be 30% or more, 40% or more, or 50% or moreof the substrate thickness. The second peak 402 and the fourth peak 404of the this example are arranged in the lower surface side oxygenreduction region 454.

Also in the this example, the first peak 401 may be arranged in theupper surface side oxygen reduction region 450. The depth position Z1 ofthe first peak 401 may be arranged closer to the upper surface 21 thanthe depth position Zc. The depth position Z1 of the first peak 401 maybe arranged closer to the upper surface 21 than the depth positionZ_(p). The depth position Z1 of the first peak 401 may be arrangedcloser to the upper surface 21 than the depth position Z_(b). The depthposition Z1 of the first peak 401 may be arranged between the depthposition Z_(p) and the depth position Z_(b).

FIG. 4 illustrates a diagram showing an example of a variation in oxygenchemical concentration distribution of the MCZ substrate before andafter oxygen annealing. Before oxygen annealing, the MCZ substrate has arelatively high oxygen chemical concentration C_(MCZ). The oxygenchemical concentration C_(MCZ) is higher than the solid solubility limitof the oxygen annealing temperature, for example. When such a substrateis subjected to oxygen annealing, oxygen in the substrate diffusesoutward, and the oxygen chemical concentration C_(OX) of the substratebecomes approximately equal to the solid solubility limit. However,since outward diffusion is promoted in the vicinity of the upper surface21 of the semiconductor substrate 10, the oxygen chemical concentrationC_(OX) decreases as approaching the upper surface 21. Note that thelower surface 23 side of the semiconductor substrate 10 of the thisexample is ground after oxygen annealing. Therefore, the oxygen chemicalconcentration C_(OX) is approximately constant on the lower surface 23side.

FIG. 5 illustrates a diagram showing an example of a variation in oxygenchemical concentration distribution of the FZ substrate before and afteroxygen annealing. Before oxygen annealing, the FZ substrate has arelatively low oxygen chemical concentration C_(FZ). The oxygen chemicalconcentration C_(FZ) is lower than the solid solubility limit of theoxygen annealing temperature, for example. When such a substrate issubjected to oxygen annealing, oxygen is introduced into the substrate,and in a region where the distance from the upper surface 21 of thesemiconductor substrate 10 is small, the oxygen chemical concentrationC_(OX) in the substrate becomes approximately equal to the solidsolubility limit. In a region where the distance from the upper surface21 is large, oxygen is difficult to be introduced, so that the oxygenchemical concentration C_(OX) gradually decreases as the distance fromthe upper surface 21 increases. Since the outward diffusion is promotedin the vicinity of the upper surface 21 of the semiconductor substrate10, the oxygen chemical concentration C_(OX) decreases as approachingthe upper surface 21. Therefore, the oxygen chemical concentrationC_(OX) may have an oxygen concentration peak 405. Note that the lowersurface 23 side of the semiconductor substrate 10 of the this example isground after oxygen annealing. Therefore, on the lower surface 23 side,the oxygen chemical concentration C_(OX) does not have a peak andgradually and monotonously decreases toward the lower surface 23.

In either one of the examples illustrated in FIG. 4 and FIG. 5, even ifthe original oxygen chemical concentration is different, the oxygenchemical concentration inside the semiconductor substrate 10 can becontrolled by the oxygen annealing temperature or the like. Therefore,it is possible to reduce variations in VOH defect concentration.

FIG. 6 illustrates a diagram showing a distribution example of therecombination center concentration N_(r) and the oxygen chemicalconcentration C_(OX). The oxygen chemical concentration C_(OX) is thesame as in the example illustrated in FIG. 2 or 3. In FIG. 6, thevicinity of the upper surface 21 is enlarged and illustrated in thedistribution of the oxygen chemical concentration C_(OX) illustrated inFIG. 3.

In the semiconductor device 100, a recombination center such as avacancy defect may be formed for the purpose of adjusting the lifetimeof the carrier. For example, the recombination center can be formed bythe implantation of charged particles such as hydrogen, helium, or anelectron beam into the semiconductor substrate 10. In the this example,the recombination center concentration N_(r) has a recombination centerpeak 406 at the depth position Z_(r). For example, a calculation methodusing well-known calculation software or tool is known as the vacancyconcentration (see, for example, http://www.srim.org/). Further, theposition of the local minimum value of the specific resistancedistribution in the depth direction of the semiconductor substrate 10may be set as the position of the recombination center peak 406.

The recombination center peak 406 may be formed in a region where theoxygen chemical concentration C_(OX) is 70% or more on the upper surface21 side of the semiconductor substrate 10. The recombination center peak406 may be combined to hydrogen to form a VOH defect. Therefore, if thevariation in the oxygen chemical concentration C_(OX) is large, theconcentration of the recombination center tends to vary, and it becomesdifficult to precisely adjust the lifetime of the carrier. In the thisexample, since the recombination center peak 406 is arranged in a regionwhere the concentration of the oxygen chemical concentration C_(OX) isrelatively stable, the concentration of the recombination center can beeasily controlled, and the lifetime of the carrier can be preciselyadjusted. The recombination center peak 406 may be formed in a regionwhere the oxygen chemical concentration C_(OX) is 80% or more of themaximum value C_(OX_max), or may be arranged in a region where theoxygen chemical concentration C_(OX) is 90% or more.

The depth position Z_(r) may be the same position as the depth positionZ1 into which the charged particle beam is implanted. That is, thecarrier lifetime may be adjusted by the implantation of the chargedparticle beam into the depth position Z1. Further, the depth positionZ_(r) may be a position near the depth position Z1 and closer to theimplantation surface of the charged particle beam (the lower surface 23in the this example) than the depth position Z1. In a case where thecharged particles implanted into the depth position Z1 are hydrogenions, recombination centers in the vicinity of the depth position Z1 arecombined to hydrogen to form VOH defects. Therefore, the concentrationof the recombination centers at the depth position Z1 decreases, and thedepth position Z_(r) shifts toward the implantation surface of thehydrogen ions (the lower surface 23 in the this example). The distancebetween the depth position Z1 and the depth position Z_(r) may be 5 μmor less, 3 μm or less, or 1 μm or less.

In another example, the depth position Z_(r) may be a position differentfrom the depth position Z1. In this case, apart from the implantation ofthe charged particle beam into the depth position Z1, the chargedparticle beam is also implanted into the depth position Z_(r). Theimplantation of the charged particle beam into the depth position Z_(r)may be performed after hydrogen annealing for diffusing hydrogenimplanted into the depth position Z2.

FIG. 7 illustrates a diagram for describing the position of the thirdpeak 403. In FIG. 7, a modification of the position of the third peak403 is illustrated as third peaks 403-1, 403-2, and 403-3. Any of thethird peaks 403 is provided in the semiconductor substrate 10. The thirdpeak 403-1 is arranged between the oxygen concentration peak 405 and theboundary position Zb. The boundary position Zb is a boundary positionbetween the maximum value region 452 of the oxygen chemicalconcentration C_(OX) and the upper surface side oxygen reduction region450. This makes it possible to form the high concentration region 460(see FIG. 2 and FIG. 3) long and to suppress variations in the value ofthe third peak 403.

The third peak 403-2 according to another example is arranged in theupper surface side oxygen reduction region 450. In this case, the highconcentration region 460 can be formed even longer. The third peak 403-3according to another example is arranged between the oxygenconcentration peak 405 and the depth position Zc. In this case, thethird peak 403-3 can be arranged in a region where the variation of theoxygen chemical concentration C_(OX) is relatively gradual. The thirdpeak 403-3 may be arranged in the maximum value region 452.

FIG. 8 illustrates an example of a top view of the semiconductor device100. FIG. 8 illustrates a position where each member is projected on theupper surface of the semiconductor substrate 10. In FIG. 8, only somemembers of the semiconductor device 100 are illustrated, and somemembers are omitted.

The semiconductor device 100 includes the semiconductor substrate 10described with reference to FIG. 1 to FIG. 7. The semiconductorsubstrate 10 has an end side 102 in the top view. When merely referredto as the top view in the present specification, it means that thesemiconductor substrate 10 is viewed from an upper surface side. Thesemiconductor substrate 10 of this example has two sets of end sides 102opposite to each other in the top view. In FIG. 1, the X axis and the Yaxis are parallel to any of the end sides 102. In addition, the Z axisis perpendicular to the upper surface of the semiconductor substrate 10.

The semiconductor substrate 10 is provided with an active portion 160.The active portion 160 is a region where a main current flows in thedepth direction between the upper surface and a lower surface of thesemiconductor substrate 10 when the semiconductor device 100 operates.An emitter electrode is provided above the active portion 160, but isomitted in FIG. 8.

The active portion 160 is provided with at least one of a transistorportion 70 including a transistor element such as an IGBT, and a diodeportion 80 including a diode element such as a freewheeling diode (FWD).In the example of FIG. 8, the transistor portion 70 and the diodeportion 80 are arranged alternately along a predetermined arraydirection (the X axis direction in the this example) in the uppersurface of the semiconductor substrate 10. The active portion 160 inanother example may be provided with only one of the transistor portion70 and the diode portion 80.

In FIG. 8, a region where the transistor portion 70 is arranged isdenoted by a symbol “I”, and a region where the diode portion 80 isarranged is denoted by a symbol “F”. In the present specification, adirection perpendicular to the array direction in a top view may bereferred to as an extending direction (Y axis direction in FIG. 8). Eachof the transistor portions 70 and the diode portions 80 may have alongitudinal length in the extending direction. In other words, thelength of each of the transistor portions 70 in the Y axis direction islarger than the width in the X axis direction. Similarly, the length ofeach of the diode portions 80 in the Y axis direction is larger than thewidth in the X axis direction. The extending direction of the transistorportion 70 and the diode portion 80, and the longitudinal direction ofeach trench portion described later may be the same.

Each of the diode portions 80 includes a cathode region of N+ type in aregion in contact with the lower surface of the semiconductor substrate10. In the present specification, a region where the cathode region isprovided is referred to as the diode portion 80. In other words, thediode portion 80 is a region that overlaps with the cathode region inthe top view. On the lower surface of the semiconductor substrate 10, acollector region of P+ type of may be provided in a region other thanthe cathode region. In the specification, the diode portion 80 may alsoinclude an extension region 81 where the diode portion 80 extends to agate runner described below in the Y axis direction. The collectorregion is provided on a lower surface of the extension region 81.

The transistor portion 70 has the collector region of the P+ type in aregion in contact with the lower surface of the semiconductor substrate10. Further, in the transistor portion 70, an emitter region of the Ntype, a base region of the P type, and a gate structure having a gateconductive portion and a gate dielectric film are periodically arrangedon the upper surface side of the semiconductor substrate 10.

The semiconductor device 100 may have one or more pads above thesemiconductor substrate 10. The semiconductor device 100 of this examplehas a gate pad 112. The semiconductor device 100 may have a pad such asan anode pad, a cathode pad, and a current detection pad. Each pad isarranged in a region close to the end side 102. The region close to theend side 102 refers to a region between the end side 102 and the emitterelectrode in the top view. In implementation of the semiconductor device100, each pad may be connected to an external circuit via wiring such asa wire.

A gate potential is applied to the gate pad 112. The gate pad 112 iselectrically connected to the conductive portion of the gate trenchportion of the active portion 160. The semiconductor device 100 includesa gate runner that connects the gate pad 112 and the gate trenchportion. In FIG. 8, the gate runner is hatched with diagonal lines.

The gate runner of this example has an outer circumferential gate runner130 and an active-side gate runner 131. The outer circumferential gaterunner 130 is arranged between the active portion 160 and the end side102 of the semiconductor substrate 10 in the top view. The outercircumferential gate runner 130 of this example encloses the activeportion 160 in the top view. A region enclosed by the outercircumferential gate runner 130 in the top view may be the activeportion 160. The outer circumferential gate runner 130 is connected tothe gate pad 112. The outer circumferential gate runner 130 is arrangedabove the semiconductor substrate 10. The outer circumferential gaterunner 130 may be a metal wiring including aluminum.

The active-side gate runner 131 is provided in the active portion 160.With the provision of the active-side gate runner 131 in the activeportion 160, it is possible to reduce a variation in wiring length fromthe gate pad 112 in each region of the semiconductor substrate 10.

The active-side gate runner 131 is connected to the gate trench portionof the active portion 160. The active-side gate runner 131 is arrangedabove the semiconductor substrate 10. The active-side gate runner 131may be a wiring formed of a semiconductor such as polysilicon doped withan impurity.

The active-side gate runner 131 may be connected to the outercircumferential gate runner 130. The active-side gate runner 131 of thisexample is provided extending in the X axis direction so as to cross theactive portion 160 from one outer circumferential gate runner 130 to theother outer circumferential gate runner 130 substantially at the centerof the Y axis direction. When the active portion 160 is divided by theactive-side gate runner 131, the transistor portion 70 and the diodeportion 80 may be alternately arranged in the X axis direction in eachdivided region.

Further, the semiconductor device 100 may include a temperature sensingportion (not shown) that is a PN junction diode formed of polysilicon orthe like, and a current detection portion (not shown) that simulates anoperation of the transistor portion provided in the active portion 160.

The semiconductor device 100 of the this example includes an edgetermination structure portion 90 between the active portion 160 and theend side 102. The edge termination structure portion 90 of this exampleis arranged between the outer circumferential gate runner 130 and theend side 102. The edge termination structure portion 90 reduces anelectric field strength on the upper surface side of the semiconductorsubstrate 10. The edge termination structure portion 90 includes aplurality of guard rings 92. The guard ring 92 is a P type region incontact with the upper surface of the semiconductor substrate 10. Theguard ring 92 may enclose the active portion 160 in a top view. Theplurality of guard rings 92 are arranged at predetermined intervalsbetween the outer circumferential gate runner 130 and the end side 102.The guard ring 92 arranged on the outer side may enclose the guard ring92 arranged on the inner side by one. The outer side refers to a sideclose to the end side 102, and the inner side refers to a side close tothe outer circumferential gate runner 130. By providing the plurality ofguard rings 92, the depletion layer on the upper surface side of theactive portion 160 can be extended outward, and the breakdown voltage ofthe semiconductor device 100 can be improved. The edge terminationstructure portion 90 may further include at least one of a field plateand a RESURF annularly provided enclosing the active portion 160.

FIG. 9 illustrates an enlarged view of a region A in FIG. 8. The regionA is a region including the transistor portion 70, the diode portion 80,and the active-side gate runner 131. The semiconductor device 100 ofthis example includes a gate trench portion 40, a dummy trench portion30, a well region 11, an emitter region 12, a base region 14, and acontact region 15 which are provided inside the upper surface side ofthe semiconductor substrate 10. Each of the gate trench portion 40 andthe dummy trench portion 30 is an example of a trench portion. Further,the semiconductor device 100 of this example includes an emitterelectrode 52 and the active-side gate runner 131 that are provided abovethe upper surface of the semiconductor substrate 10. The emitterelectrode 52 and the active-side gate runner 131 are provided inisolation each other.

An interlayer dielectric film is provided between the emitter electrode52 and the active-side gate runner 131, and the upper surface of thesemiconductor substrate 10, but is omitted in FIG. 9. In the interlayerdielectric film of this example, a contact hole 54 is provided passingthrough the interlayer dielectric film. In FIG. 9, each contact hole 54is hatched with diagonal lines.

The emitter electrode 52 is provided on the upper side of the gatetrench portion 40, the dummy trench portion 30, the well region 11, theemitter region 12, the base region 14, and the contact region 15. Theemitter electrode 52 is in contact with the emitter region 12, thecontact region 15, and the base region 14 on the upper surface of thesemiconductor substrate 10, through the contact hole 54. Further, theemitter electrode 52 is connected to a dummy conductive portion in thedummy trench portion 30 through the contact hole provided in theinterlayer dielectric film. The emitter electrode 52 may be connected tothe dummy conductive portion of the dummy trench portion 30 at an edgeof the dummy trench portion 30 in the Y axis direction.

The active-side gate runner 131 is connected to the gate trench portion40 through the contact hole provided in the interlayer dielectric film.The active-side gate runner 131 may be connected to a gate conductiveportion of the gate trench portion 40 at an edge portion 41 of the gatetrench portion 40 in the Y axis direction. The active-side gate runner131 is not connected to the dummy conductive portion in the dummy trenchportion 30.

The emitter electrode 52 is formed of a material including a metal. FIG.9 illustrates a range in which the emitter electrode 52 is provided. Forexample, at least a partial region of the emitter electrode 52 is formedof aluminum or an aluminum-silicon alloy, for example, a metal alloysuch as AlSi or AlSiCu. The emitter electrode 52 may have a barriermetal formed of titanium, a titanium compound, or the like below aregion formed of aluminum or the like. Further, a plug, which is formedby embedding tungsten or the like so as to be in contact with thebarrier metal and aluminum or the like, may be included in the contacthole.

The well region 11 is provided overlapping the active-side gate runner131. The well region 11 is provided so as to extend with a predeterminedwidth even in a range not overlapping the active-side gate runner 131.The well region 11 of this example is provided away from an end of thecontact hole 54 in the Y axis direction toward the active-side gaterunner 131 side. The well region 11 is a second conductivity type regionin which the doping concentration is higher than the base region 14. Thebase region 14 of this example is a P− type, and the well region 11 is aP+ type.

Each of the transistor portion 70 and the diode portion 80 includes aplurality of trench portions arranged in the array direction. In thetransistor portion 70 of this example, one or more gate trench portions40 and one or more dummy trench portions 30 are alternately providedalong the array direction. In the diode portion 80 of this example, theplurality of dummy trench portions 30 are provided along the arraydirection. In the diode portion 80 of this example, the gate trenchportion 40 is not provided.

The gate trench portion 40 of this example may have two linear portions39 extending along the extending direction perpendicular to the arraydirection (portions of a trench that are linear along the extendingdirection), and the edge portion 41 connecting the two linear portions39. The extending direction in FIG. 9 is the Y axis direction.

At least a part of the edge portion 41 is preferably provided in acurved shape in a top view. By connecting between end portions of thetwo linear portions 39 in the Y axis direction by the edge portion 41,it is possible to reduce the electric field strength at the end portionsof the linear portions 39.

In the transistor portion 70, the dummy trench portions 30 are providedbetween the respective linear portions 39 of the gate trench portions40. Between the respective linear portions 39, one dummy trench portion30 may be provided or a plurality of dummy trench portions 30 may beprovided. The dummy trench portion 30 may have a linear shape extendingin the extending direction, or may have linear portions 29 and an edgeportion 31 similar to the gate trench portion 40. The semiconductordevice 100 illustrated in FIG. 9 includes both the linear dummy trenchportion 30 not having the edge portion 31 and the dummy trench portion30 having the edge portion 31.

A diffusion depth of the well region 11 may be deeper than the depth ofthe gate trench portion 40 and the dummy trench portion 30. The endportions in the Y axis direction of the gate trench portion 40 and thedummy trench portion 30 are provided in the well region 11 in a topview. In other words, the bottom in the depth direction of each trenchportion is covered with the well region 11 at the end portion in the Yaxis direction of each trench portion. With this configuration, theelectric field strength on the bottom portion of each trench portion canbe reduced.

A mesa portion is provided between the respective trench portions in thearray direction. The mesa portion refers to a region sandwiched betweenthe trench portions inside the semiconductor substrate 10. As anexample, an upper end of the mesa portion is the upper surface of thesemiconductor substrate 10. The depth position of the lower end of themesa portion is the same as the depth position of the lower end of thetrench portion. The mesa portion of this example is provided extendingin the extending direction (the Y axis direction) along the trenchportion, on the upper surface of the semiconductor substrate 10. In thisexample, a mesa portion 60 is provided in the transistor portion 70, anda mesa portion 61 is provided in the diode portion 80. In the case ofsimply mentioning “mesa portion” in the present specification, theportion refers to each of the mesa portion 60 and the mesa portion 61.

Each mesa portion is provided with the base region 14. In the mesaportion, a region arranged closest to the active-side gate runner 131,in the base region 14 exposed on the upper surface of the semiconductorsubstrate 10, is to be a base region 14-e. In FIG. 9, the base region14-e arranged at one end portion of each mesa portion in the extendingdirection is illustrated, but the base region 14-e is also arranged atthe other end portion of each mesa portion. Each mesa portion may beprovided with at least one of a first conductivity type of emitterregion 12, and a second conductivity type of contact region 15 in aregion sandwiched between the base regions 14-e in the top view. Theemitter region 12 of this example is an N+ type, and the contact region15 is a P+ type. The emitter region 12 and the contact region 15 may beprovided between the base region 14 and the upper surface of thesemiconductor substrate 10 in the depth direction.

The mesa portion 60 of the transistor portion 70 has the emitter region12 exposed on the upper surface of the semiconductor substrate 10. Theemitter region 12 is provided in contact with the gate trench portion40. The mesa portion 60 in contact with the gate trench portion 40 maybe provided with the contact region 15 exposed on the upper surface ofthe semiconductor substrate 10.

Each of the contact region 15 and the emitter region 12 in the mesaportion 60 is provided from one trench portion to the other trenchportion in the X axis direction. As an example, the contact region 15and the emitter region 12 in the mesa portion 60 are alternatelyarranged along the extending direction of the trench portion (the Y axisdirection).

In another example, the contact region 15 and the emitter region 12 inthe mesa portion 60 may be provided in a stripe shape along theextending direction of the trench portion (the Y axis direction). Forexample, the emitter region 12 is provided in a region in contact withthe trench portion, and the contact region 15 is provided in a regionsandwiched between the emitter regions 12.

The mesa portion 61 of the diode portion 80 is not provided with theemitter region 12. The base region 14 and the contact region 15 may beprovided on an upper surface of the mesa portion 61. In the regionsandwiched between the base regions 14-e on the upper surface of themesa portion 61, the contact region 15 may be provided in contact witheach base region 14-e. The base region 14 may be provided in a regionsandwiched between the contact regions 15 on the upper surface of themesa portion 61. The base region 14 may be arranged in the entire regionsandwiched between the contact regions 15.

The contact hole 54 is provided above each mesa portion. The contacthole 54 is arranged in the region sandwiched between the base regions14-e. The contact hole 54 of this example is provided above respectiveregions of the contact region 15, the base region 14, and the emitterregion 12. The contact hole 54 is not provided in regions correspondingto the base region 14-e and the well region 11. The contact hole 54 maybe arranged at the center of the mesa portion 60 in the array direction(the X axis direction).

In the diode portion 80, a cathode region 82 of the N+ type is providedin a region in direct contact with the lower surface of thesemiconductor substrate 10. On the lower surface of the semiconductorsubstrate 10, a collector region of the P+ type 22 may be provided in aregion where the cathode region 82 is not provided. In FIG. 9, theboundary between the cathode region 82 and the collector region 22 isindicated by a dotted line.

The cathode region 82 is arranged separately from the well region 11 inthe Y axis direction. With this configuration, the distance between theP type region (the well region 11) having a relatively high dopingconcentration and formed up to the deep position, and the cathode region82 is ensured, so that the breakdown voltage can be improved. The endportion in the Y axis direction of the cathode region 82 of this exampleis arranged farther away from the well region 11 than the end portion inthe Y axis direction of the contact hole 54. In another example, the endportion in the Y axis direction of the cathode region 82 may be arrangedbetween the well region 11 and the contact hole 54.

FIG. 10 illustrates a diagram showing an example of a cross section b-bin FIG. 9. The cross section b-b is an XZ plane passing through theemitter region 12 and the cathode region 82. The semiconductor device100 of this example includes the semiconductor substrate 10, theinterlayer dielectric film 38, the emitter electrode 52, and thecollector electrode 24 in the cross section. The interlayer dielectricfilm 38 is provided on the upper surface of the semiconductor substrate10. The interlayer dielectric film 38 is a film including at least onelayer of a dielectric film such as silicate glass to which an impuritysuch as boron or phosphorous is added, a thermal oxide film, and otherdielectric films. The interlayer dielectric film 38 is provided with thecontact hole 54 described in FIG. 9.

The emitter electrode 52 is provided on the upper side of the interlayerdielectric film 38. The emitter electrode 52 is in contact with an uppersurface 21 of the semiconductor substrate 10 through the contact hole 54of the interlayer dielectric film 38. The collector electrode 24 isprovided on a lower surface 23 of the semiconductor substrate 10. Theemitter electrode 52 and the collector electrode 24 are made of a metalmaterial such as aluminum. In the specification, the direction in whichthe emitter electrode 52 is connected to the collector electrode 24 (theZ axis direction) is referred to as a depth direction.

The semiconductor substrate 10 has an N− type bulk doping region 18. Thebulk doping region 18 is a region where the doping concentration of thebulk doping region 18 matches the donor concentration of the bulk donor.The bulk doping region 18 is provided in each of the transistor portion70 and the diode portion 80.

In the mesa portion 60 of the transistor portion 70, an N+ type ofemitter region 12 and a P− type of base region 14 are provided in orderfrom an upper surface 21 side of the semiconductor substrate 10. Thebulk doping region 18 is provided below the base region 14. The mesaportion 60 may be provided with an N+ type of accumulation region 16.The accumulation region 16 is arranged between the base region 14 andthe bulk doping region 18.

The emitter region 12 is exposed on the upper surface 21 of thesemiconductor substrate 10 and is provided in contact with gate trenchportion 40. The emitter region 12 may be in contact with the trenchportions on both sides of the mesa portion 60. The emitter region 12 hasa higher doping concentration than the bulk doping region 18.

The base region 14 is provided below the emitter region 12. The baseregion 14 of this example is provided in contact with the emitter region12. The base region 14 may be in contact with the trench portions onboth sides of the mesa portion 60.

The accumulation region 16 is provided below the base region 14. Theaccumulation region 16 is an N+ type region having a higher dopingconcentration than the bulk doping region 18. By providing thehigh-concentration accumulation region 16 between the bulk doping region18 and the base region 14, the implantation enhancement effect (IEeffect) of the carrier can be improved, and the ON voltage can bereduced. The accumulation region 16 may be provided to cover a wholelower surface of the base region 14 in each mesa portion 60.

The mesa portion 61 of the diode portion 80 is provided with the P− typeof base region 14 in contact with the upper surface 21 of thesemiconductor substrate 10. The bulk doping region 18 is provided belowthe base region 14. In the mesa portion 61, the accumulation region 16may be provided below the base region 14.

In each of the transistor portion 70 and the diode portion 80, an N+type buffer region 20 may be provided on the lower surface 23 side withrespect to the bulk doping region 18 and the high concentration region460. The doping concentration of the buffer region 20 is higher than thedoping concentration of the bulk doping region 18. The buffer region 20has one or more donor concentration peaks with higher donorconcentrations than the bulk doping region 18. The plurality of donorconcentration peaks are arranged at different positions in the depthdirection of the semiconductor substrate 10. The donor concentrationpeak of the buffer region 20 may be, for example, a concentration peakof hydrogen (proton) or phosphorous. The buffer region 20 may includethe second peak 402 of hydrogen chemical concentration (see FIG. 2 andthe like). The buffer region 20 may function as a field stopper layerwhich prevents a depletion layer expanding from the lower end of thebase region 14 from reaching the collector region of the P+ type 22 andthe cathode region 82 of the N+ type 82.

In the transistor portion 70, the collector region of the P+ type 22 isprovided below the buffer region 20. An acceptor concentration of thecollector region 22 is higher than an acceptor concentration of the baseregion 14. The collector region 22 may include an acceptor which is thesame as or different from an acceptor of the base region 14. Theacceptor of the collector region 22 is, for example, boron.

Below the buffer region 20 in the diode portion 80, the cathode region82 of the N+ type is provided. The donor concentration of the cathoderegion 82 is higher than the donor concentration of the bulk dopingregion 18. A donor of the cathode region 82 is, for example, hydrogen orphosphorous. Note that an element serving as a donor and an acceptor ineach region is not limited to the above described example. The collectorregion 22 and the cathode region 82 are exposed on the lower surface 23of the semiconductor substrate 10 and are connected to the collectorelectrode 24. The collector electrode 24 may be in contact with theentire lower surface 23 of the semiconductor substrate 10. The emitterelectrode 52 and the collector electrode 24 are formed of a metalmaterial such as aluminum.

One or more gate trench portions 40 and one or more dummy trenchportions 30 are provided on the upper surface 21 side of thesemiconductor substrate 10. Each trench portion penetrates the baseregion 14 from the upper surface 21 of the semiconductor substrate 10 toreach the bulk doping region 18. In the region where at least one of theemitter region 12, the contact region 15, and the accumulation region 16is provided, each trench portion also penetrates these doping regionsand reaches the bulk doping region 18. The configuration of the trenchportion penetrating the doping region is not limited to the onemanufactured in the order of forming the doping region and then formingthe trench portion. The configuration of the trench portion penetratingthe doping region includes a configuration of the doping region beingformed between the trench portions after forming the trench portion.

As described above, the transistor portion 70 is provided with the gatetrench portion 40 and the dummy trench portion 30. In the diode portion80, the dummy trench portion 30 is provided, and the gate trench portion40 is not provided. The boundary in the X axis direction between thediode portion 80 and the transistor portion 70 in this example is theboundary between the cathode region 82 and the collector region 22.

The gate trench portion 40 includes a gate trench provided in the uppersurface 21 of the semiconductor substrate 10, a gate dielectric film 42,and a gate conductive portion 44. The gate dielectric film 42 isprovided to cover the inner wall of the gate trench. The gate dielectricfilm 42 may be formed by oxidizing or nitriding a semiconductor on theinner wall of the gate trench. The gate conductive portion 44 isprovided inside from the gate dielectric film 42 in the gate trench.That is, the gate dielectric film 42 insulates the gate conductiveportion 44 from the semiconductor substrate 10. The gate conductiveportion 44 is formed of a conductive material such as polysilicon.

The gate conductive portion 44 may be provided longer than the baseregion 14 in the depth direction. The gate trench portion 40 in thecross section is covered by the interlayer dielectric film 38 on theupper surface 21 of the semiconductor substrate 10. The gate conductiveportion 44 is electrically connected to the gate runner. When apredetermined gate voltage is applied to the gate conductive portion 44,a channel is formed by an electron inversion layer in a surface layer ofthe base region 14 at a boundary in contact with the gate trench portion40.

The dummy trench portions 30 may have the same structure as the gatetrench portions 40 in the cross section. The dummy trench portion 30includes a dummy trench provided in the upper surface 21 of thesemiconductor substrate 10, a dummy dielectric film 32, and a dummyconductive portion 34. The dummy conductive portion 34 may be connectedto an electrode different from the gate pad. For example, the dummyconductive portion 34 may be connected to a dummy pad (not illustrated)connected to an external circuit different from the gate pad, andcontrol different from that of the gate conductive portion 44 may beperformed. The dummy conductive portion 34 may be electrically connectedto the emitter electrode 52. The dummy dielectric film 32 is providedcovering an inner wall of the dummy trench. The dummy conductive portion34 is provided in the dummy trench, and is provided inside the dummydielectric film 32. The dummy dielectric film 32 insulates the dummyconductive portion 34 from the semiconductor substrate 10. The dummyconductive portion 34 may be formed of the same material as the gateconductive portion 44. For example, the dummy conductive portion 34 isformed of a conductive material such as polysilicon or the like. Thedummy conductive portion 34 may have the same length as the gateconductive portion 44 in the depth direction.

The gate trench portion 40 and the dummy trench portion 30 of thisexample are covered with the interlayer dielectric film 38 on the uppersurface 21 of the semiconductor substrate 10. It is noted that thebottoms of the dummy trench portion 30 and the gate trench portion 40may be formed in a curved-surface shape (a curved-line shape in thecross section) convexly downward.

The semiconductor substrate 10 has distributions of the oxygen chemicalconcentration C_(OX), the impurity chemical concentration C_(I), thehydrogen chemical concentration C_(H), and the VOH defect concentrationN_(VOH) similar to any of the examples described in FIG. 1 to FIG. 6. InFIG. 10, the first peak 401 is indicated by a cross mark, and the highconcentration region 460 is hatched with diagonal lines. The bufferregion 20, the cathode region 82, and the collector region 22 may alsobe included in the high concentration region 460, but diagonal line isomitted in FIG. 10. The high concentration region 460 may be providedfrom the first peak 401 to the lower surface 23.

As described above, the high concentration region 460 includes VOHdefects. The bulk doping region 18 and the high concentration region 460may be collectively referred to as a drift region 19. The drift region19 may be a region in which a depletion layer expands when a voltage isapplied to the semiconductor device 100 and which supports half or moreof the applied voltage.

FIG. 11 illustrates a diagram showing an example of a cross section c-cin FIG. 8. The cross section c-c is an XZ plane passing through the edgetermination structure portion 90, the transistor portion 70, and thediode portion 80. The structures of the transistor portion 70 and thediode portion 80 are the same as those of the transistor portion 70 andthe diode portion 80 described in FIG. 9 and FIG. 10. In FIG. 11, thestructures of the gate trench portion 40 and the dummy trench portion 30are illustrated in a simplified manner.

In the semiconductor substrate 10, the well region 11 is providedbetween the edge termination structure portion 90 and the transistorportion 70. The well region 11 is a P+ type region in contact with theupper surface 21 of the semiconductor substrate 10. The well region 11may be provided up to a position deeper than the lower ends of the gatetrench portion 40 and the dummy trench portion 30. A part of the gatetrench portion 40 and a part of the dummy trench portion 30 may bearranged inside the well region 11.

An interlayer dielectric film 38 covering the well region 11 may beprovided in the upper surface 21 of the semiconductor substrate 10.Above the interlayer dielectric film 38, electrodes and wiring such asthe emitter electrode 52 and the outer circumferential gate runner 130are provided. The emitter electrode 52 is provided extending from abovethe active portion 160 to above the well region 11. The emitterelectrode 52 may be connected to the well region 11 via a contact holeprovided in the interlayer dielectric film 38.

The outer circumferential gate runner 130 is arranged between theemitter electrode 52 and the edge termination structure portion 90.Although the emitter electrode 52 and the outer circumferential gaterunner 130 are arranged separately from each other, a gap between theemitter electrode 52 and the outer circumferential gate runner 130 isomitted in FIG. 11. The outer circumferential gate runner 130 iselectrically insulated from the well region 11 by the interlayerdielectric film 38.

The edge termination structure portion 90 is provided with a pluralityof guard rings 92, a plurality of second high concentration regions 202,a plurality of field plates 94, and a channel stopper 174. In addition,the first peak 401 and the high concentration region 460 are alsoprovided in at least a part of the edge termination structure portion90. The high concentration region 460 may be provided below the guardring 92. The first peak 401 and the high concentration region 460 of theedge termination structure portion 90 may be provided continuously withthe first peak 401 and the high concentration region 460 of thetransistor portion 70 and the diode portion 80. The first peak 401 andthe high concentration region 460 may be provided over the entire edgetermination structure portion 90 in the X axis direction.

The first peak 401 of the this example is provided below the second highconcentration region 202 (that is, a position deeper than the secondhigh concentration region 202 as viewed from the upper surface 21)described later. The first peak 401 may be arranged at a position deeperthan the lower end of the guard ring 92. That is, first peak 401 may bearranged between the lower end of guard ring 92 and lower surface 23 ofsemiconductor substrate 10. The first peak 401 may be arranged at aposition deeper than the lower end of the well region 11. The first peak401 may be arranged at a position deeper than the lower end of thetrench portion.

Although the high concentration region 460 illustrated in FIG. 11 is notin contact with the guard ring 92, the high concentration region 460 maybe in contact with the lower end of the guard ring 92. The highconcentration region 460 may be provided up to between the two guardrings 92. The high concentration region 460 may or may not be in contactwith the well region 11. The high concentration region 460 may or maynot be in contact with the trench portion. The high concentration region460 may be provided below the second high concentration region 202.

The high concentration region 460 may be in contact with the well region11. The high concentration region 460 may be in contact with the trenchportion. The high concentration region 460 may not be in contact withany of the emitter region 12, the base region 14, and the accumulationregion 16. In another example, the high concentration region 460 may bein contact with the accumulation region 16. The high concentrationregion 460 may be in contact with the base region 14. The highconcentration region 460 may not be in contact with or may be in contactwith the channel stopper 174.

The high concentration regions 460 may have the same or differentlengths in the depth direction throughout the edge termination structureportion 90. In the high concentration region 460, the edge terminationstructure portion 90 and the active portion 160 may have the same ordifferent lengths in the depth direction.

In the edge termination structure portion 90, a collector region 22 maybe provided in a region in contact with the lower surface 23. Each guardring 92 may be provided to enclose the active portion 160 in the uppersurface 21. The plurality of guard rings 92 may have a function ofexpanding the depletion layer generated in the active portion 160 to theoutside of the semiconductor substrate 10. As a result, electric fieldstrength inside the semiconductor substrate 10 can be prevented, and thebreakdown voltage of the semiconductor device 100 can be improved.

The guard ring 92 of the this example is a P+ type semiconductor regionformed by the implantation of ions in the vicinity of the upper surface21. The guard ring 92 can be formed by selectively implanting a P typedopant such as boron from the upper surface 21 of the semiconductorsubstrate 10 and performing heat treatment. The depth of the bottomportion of the guard ring 92 may be deeper than the depths of the bottomportions of the gate trench portion 40 and the dummy trench portion 30.The depth of the bottom portion of the guard ring 92 may be the same asor different from the depth of the bottom portion of the well region 11.

The upper surface of the guard ring 92 is covered with the interlayerdielectric film 38. The field plate 94 is formed of a metal such asaluminum or a conductive material such as polysilicon. The field plate94 may be formed of an aluminum-silicon alloy, for example, a metalalloy such as AlSi or AlSiCu. The field plate 94 may be formed of thesame material as the outer circumferential gate runner 130 or theemitter electrode 52. The field plate 94 is provided on the interlayerdielectric film 38. The field plate 94 of the this example is connectedto the guard ring 92 through a through hole provided in the interlayerdielectric film 38.

The channel stopper 174 is an N type or P type region arranged furtheroutside the outermost guard ring 92 and exposed to the upper surface 21of the semiconductor substrate 10. Note that the term “outside” refersto a side on which the distance from the active portion 160 increases ina top view. That is, the outermost guard ring 92 refers to the guardring 92 farthest from the active portion 160 in the X axis direction.The channel stopper 174 of the this example is provided to be exposed tothe upper surface 21 and the side wall in the vicinity of the end side102 of the semiconductor substrate 10. The channel stopper 174 is an Ntype region having a doping concentration higher than that of the bulkdoping region 18. The doping concentration of the channel stopper 174may be higher than the doping concentration of the high concentrationregion 460. The channel stopper 174 has a function of terminating thedepletion layer, which is generated in the active portion 160, in thevicinity of the end side 102 of the semiconductor substrate 10. Notethat, although at least a part of the field plate 94, the outercircumferential gate runner 130, and the emitter electrode 52 is coveredwith a protective film such as a polyimide or nitride film, theprotective film may be omitted in the drawings of the presentspecification.

The second high concentration region 202 is an N type region having adonor concentration higher than the doping concentration of the bulkdonor. The second high concentration region 202 is provided between twoadjacent guard rings 92. The second high concentration region 202 may bein contact with the upper surface 21 of the semiconductor substrate 10.The second high concentration region 202 of the this example is providedin a range shallower than the lower end of the guard ring 92 from theupper surface 21. In another example, the second high concentrationregion 202 may be provided to a position deeper than the lower end ofguard ring 92. The second high concentration region 202 may also beprovided between the well region 11 and the guard ring 92.

The second high concentration region 202 may be formed by implanting adonor from the upper surface 21 of the semiconductor substrate 10 usingthe field plate 94 as a mask and performing heat treatment. In thiscase, at least a part of the second high concentration region 202 isformed in a region not covered with the field plate 94. At least a partof the second high concentration region 202 of the this example does notoverlap the field plate 94 in the Z axis direction. The donor to beimplanted into the second high concentration region 202 may bephosphorous, hydrogen, or another donor. In a case where the second highconcentration region 202 is formed deep, the donor may be implanted intoa plurality of depth positions by varying the acceleration energy of thedonor.

In another example, the second high concentration region 202 may beformed by implanting the donor from the upper surface 21 of thesemiconductor substrate 10 without using the field plate 94 as a maskand performing heat treatment. In this case, boron is selectivelyion-implanted as a P type dopant, and the guard ring is formed by heattreatment. Thereafter, phosphorous is ion-implanted as an N type dopant,and the second high concentration region 202 is formed by heattreatment. The temperature of the heat treatment after the implantationof the P type dopant is higher than the temperature of the heattreatment after the implantation of the N type dopant. The dosing amountin the ion implantation of the N type dopant may be lower than thedosing amount of the P type dopant. In this case, the ion implantationof the N type dopant may also be implanted into the region forming theguard ring, or may be selectively implanted so as to avoid the regionforming the guard ring.

In the example of FIG. 11, the second high concentration region 202 andthe high concentration region 460 are arranged away from each other inthe Z axis direction. A region having the same donor concentration asthe bulk donor concentration may be provided between the second highconcentration region 202 and the high concentration region 460.

Note that, if the heat treatment is performed at a high temperature fora long time after hydrogen is implanted, the hydrogen donor disappearsor the lifetime adjustment function at the first peak 401 disappears.Therefore, it is preferable that the implantation of hydrogen and theheat treatment step are performed at the end of the manufacturing stepof the semiconductor device 100. For example, by implanting hydrogenafter forming a protective film above the field plate 94 or the like,the disappearance of hydrogen donors can be suppressed.

If the doping concentration on the upper surface 21 side of the edgetermination structure portion 90 varies, the degree of expanding of thedepletion layer in the edge termination structure portion 90 alsovaries. In a case where the second high concentration region 202 and thehigh concentration region 460 are not provided, the bulk doping region18 of the bulk donor concentration occupies a large region on the uppersurface 21 side of the edge termination structure portion 90. Since thebulk donor concentration is the concentration of the donor containedfrom the time of manufacturing the semiconductor substrate 10, variationis relatively likely to occur.

On the other hand, the second high concentration region 202 and the highconcentration region 460 are formed by the implantation of ions or thelike. Since the concentration of the implantation of ions is relativelyeasily controlled, the variation in donor concentration between thesecond high concentration region 202 and the high concentration region460 is relatively small. Therefore, by providing the second highconcentration region 202 and the high concentration region 460, it ispossible to reduce the variation in the degree of expanding in the Xaxis direction of the depletion layer extending from below the wellregion 11 to the edge termination structure portion 90, and it is alsopossible to reduce the variation in the breakdown voltage of thesemiconductor device 100. In addition, by providing the second highconcentration region 202 and the high concentration region 460, it ispossible to prevent the depletion layer from expanding too much in the Xaxis direction in the edge termination structure portion 90.

FIG. 12 illustrates the distribution examples of the carrierconcentration N_(c), the phosphorous chemical concentration C_(P), theVOH defect concentration N_(VOH), and the impurity chemicalconcentration C_(I) along the d-d line illustrated in FIG. 11. Theimpurity of the this example is hydrogen. That is, the impurity chemicalconcentration C_(I) indicates a hydrogen chemical concentration. The d-dline passes through the second high concentration region 202, the bulkdoping region 18, the high concentration region 460, the buffer region20, and the collector region 22 in the edge termination structureportion 90. The carrier concentration distribution may be the same asthe net doping concentration distribution.

In the this example, the bulk donor is phosphorous. In addition, thesecond high concentration region 202 is formed by implanting phosphorousfrom the upper surface 21 of the semiconductor substrate 10. In the thisexample, the bulk donor concentration is N_(B). The bulk donorconcentration is substantially uniform throughout the depth direction.As the bulk donor concentration, a minimum value of the concentration ofdonors distributed throughout the semiconductor substrate 10 may beused. For example, in a case where phosphorous is distributed over theentire semiconductor substrate 10, the bulk donor concentration may bethe minimum value of the phosphorous concentration in the semiconductorsubstrate 10.

The phosphorous concentration distribution in the second highconcentration region 202 has a phosphorous concentration peak 318 atwhich the phosphorous concentration becomes a local maximum value. Thedepth position of the phosphorous concentration peak 318 corresponds tothe phosphorous implantation position. The hydrogen chemicalconcentration in the high concentration region 460 has a local maximumvalue at the first peak 401.

The VOH defect density distribution may be a distribution reflecting thehydrogen chemical concentration distribution or a distribution similarto the hydrogen chemical concentration distribution. For example, thepositions of inflection points such as local maximum, local minimum, andkink of each distribution may be arranged at approximately the samedepth position. Approximately the same depth position may have an errorsmaller than the full width at half maximum of the first peak 401, forexample.

The carrier concentration distribution of the this example has a peak408 at the same depth position as the first peak 401. In the second highconcentration region 202, a peak 314 is present at the same depthposition as the phosphorous concentration peak 318. In a case where thedistance between the peaks 408 and 314 is sufficiently large, the bulkdoping region 18 having a base carrier concentration N₀₀ according tothe bulk donor concentration N_(B) is provided between the peaks 314 and408.

The high concentration region 460 may have a flat portion 313 having asubstantially uniform carrier concentration between the first peak 401and the buffer region 20. In the flat portion 313, the carrierconcentration may vary in a range from a minimum value N₀ of the carrierconcentration between the first peak 401 and the buffer region 20 to 2times or less of the minimum value N₀. In the flat portion 313, thecarrier concentration may vary in a range of the minimum value N₀ ormore and 1.5 times or less of the minimum value N₀, and the carrierconcentration may vary in a range of the minimum value N₀ or more and1.2 times or less of the minimum value N₀. The length of the flatportion 313 in the Z axis direction may be half or more of the length ofthe high concentration region 460 in the Z axis direction. In the highconcentration region 460, the carrier concentration may graduallydecrease from the peak 408 toward the buffer region 20.

The distribution of the VOH defect concentration N_(VOH) may also have aflat portion 323 at the same depth position as the flat portion 313. Inthe flat portion 323, similarly to the flat portion 313, the VOH defectdensity may vary in a range from a minimum value or more of the VOHdefect density between the first peak 401 and the buffer region 20 to 2times or less of the minimum value. In the flat portion 323, the VOHdefect density may vary in a range from the minimum value or more to 1.5times or less of the minimum value, and the VOH defect density may varyin a range from the minimum value or more to 1.2 times or less of theminimum value. The length of the flat portion 323 in the Z axisdirection may be half or more of the length of the high concentrationregion 460 in the Z axis direction.

A peak value N₁ of the carrier concentration in the second highconcentration region 202 is larger than the minimum value N₀ of thecarrier concentration in the high concentration region 460. The peakvalue N₁ may be 2 times or more, 5 times or more, or 10 times or more ofthe minimum value N₀. The peak value N₁ may be 10 times or more, or 100times or more of the base carrier concentration N₀₀.

The buffer region 20 of the this example has a plurality of donorconcentration peaks 407 having different depth positions. At least onedonor concentration peak 407 may be the concentration peak of thehydrogen donor. That is, a peak of the hydrogen chemical concentrationmay be provided at the same depth position as the donor concentrationpeak 407. The peak of the hydrogen chemical concentration functions asthe second peak 402 described in FIG. 2 and the like. All the donorconcentration peaks 407 may be hydrogen donor concentration peaks.

FIG. 13A illustrates a diagram showing another example of the crosssection c-c in FIG. 8. The semiconductor device 100 of the this exampleis different from the example illustrated in FIG. 11 in the range in thedepth direction in which the high concentration region 460 is provided.The position of the first peak 401 in the depth direction may also bedifferent from the example illustrated in FIG. 11. Other structures arethe same as those in the example illustrated in FIG. 11.

The high concentration region 460 in the this example is in contact withthe guard ring 92. The high concentration region 460 includes at least alower end of the guard ring 92. The high concentration region 460 mayalso be provided between two guard rings 92 adjacent to each other. Thehigh concentration region 460 of the this example is not in contact withthe second high concentration region 202. The high concentration region460 may be provided on the upper surface 21 side with respect to thebottom surface of the trench portion. That is, the high concentrationregion 460 may be provided up to the mesa portion sandwiched between theadjacent trench portions. The bulk doping region 18 of bulk donorconcentration may be provided between the high concentration region 460and the second high concentration region 202.

The first peak 401 of the this example is in contact with the guard ring92. That is, the first peak 401 is arranged above the lower end of theguard ring 92.

According to the this example, since the high concentration region 460covers the lower end of the guard ring 92, it is possible to reduce thevariation in the donor concentration in the region where the electricfield is likely to concentrate. Therefore, the variation in thebreakdown voltage can be further reduced.

FIG. 13B illustrates a diagram showing another example of the crosssection c-c in FIG. 8. The semiconductor device 100 of the this exampleis different from the example illustrated in FIG. 13A in the range inthe depth direction in which the high concentration region 460 isprovided. The position of the first peak 401 in the depth direction mayalso be different from the example illustrated in FIG. 13A. Otherstructures may be the same as the example illustrated in FIG. 13A.

The channel stopper 174 of the this example contains hydrogen. In thethis example, the first peak 401 is arranged at a depth positionoverlapping the channel stopper 174. Similarly, the peak of the hydrogenchemical concentration is arranged at a position overlapping the channelstopper 174. That is, hydrogen is distributed from the lower surface 23of the semiconductor substrate 10 to the depth position overlapping thechannel stopper 174. Hydrogen may be contained in the emitter region 12,the contact region 15, the base region 14, or the accumulation region16. The first peak 401 may overlap the emitter region 12, the contactregion 15, the base region 14, or the accumulation region 16.

The high concentration region 460 is provided up to the depth positionoverlapping the channel stopper 174. The high concentration region 460may be provided up to the upper surface 21 of the semiconductorsubstrate 10, or may be provided up to a position below the uppersurface 21. In the region sandwiched by the two guard rings 92, thesecond high concentration region 202 may be provided between the highconcentration region 460 and the upper surface 21, and the bulk dopingregion 18 may be provided.

In a region below the channel stopper 174 of the this example, the highconcentration region 460 is provided, and the bulk doping region 18 doesnot remain. Therefore, it is possible to suppress the depletion layerexpanding in the X axis direction from extending to the outside of thechannel stopper 174.

FIG. 13C illustrates a diagram showing another example of the crosssection c-c in FIG. 8. The semiconductor device 100 of the this exampleis different from the example illustrated in FIG. 13A or FIG. 13B in therange in the depth direction in which the high concentration region 460is provided. In addition, the first peak 401 does not exist in thesemiconductor substrate 10. Other structures may be the same as theexamples illustrated in FIG. 13A or FIG. 13B.

In the this example, impurities (hydrogen) are implanted from the lowersurface 23 or the upper surface 21 of the semiconductor substrate 10 soas to penetrate the semiconductor substrate 10. That is, theacceleration energy of hydrogen ions is adjusted so that the range ofhydrogen ions is larger than the thickness of the semiconductorsubstrate 10. Therefore, the first peak 401 is not provided in thesemiconductor substrate 10. At the time of hydrogen ion implantation, anabsorber such as a shielding member 350 described later may be used ormay not be used.

The high concentration region 460 is formed from the lower surface 23 tothe upper surface 21 of the semiconductor substrate 10. In the thisexample, the second high concentration region 202 may not be provided,and the second high concentration region 202 may be provided so as tooverlap the high concentration region 460.

In a region below the channel stopper 174 of the this example, the highconcentration region 460 is provided, and the bulk doping region 18 doesnot remain. Therefore, it is possible to suppress the depletion layerexpanding in the X axis direction from extending to the outside of thechannel stopper 174. In addition, since the first peak 401 does notexist, the influence on the doping region (for example, the emitterregion 12, the base region 14, the contact region 15, the accumulationregion 16, the well region 11, and the guard ring 92) locally providedon the upper surface 21 side of the semiconductor substrate 10 can bereduced.

FIG. 14 illustrates a diagram showing another example of the crosssection c-c in FIG. 8. The semiconductor device 100 of the this exampleis different from the example illustrated in FIG. 11, FIG. 13A, FIG.13B, or FIG. 13C in the range in the depth direction in which the secondhigh concentration region 202 and the high concentration region 460 areprovided. Other structures are the same as the example illustrated inFIG. 11, FIG. 13A, FIG. 13B, or FIG. 13C.

A part of the second high concentration region 202 and a part of thehigh concentration region 460 of the this example are provided in thesame region. The lower end of the second high concentration region 202is arranged within the range of the high concentration region 460, andthe upper end of the high concentration region 460 is arranged withinthe range of the second high concentration region 202. With thisconfiguration, the region of the bulk donor concentration in the edgetermination structure portion 90 can be reduced by connecting the secondhigh concentration region 202 and the high concentration region 460.Therefore, the variation in breakdown voltage can be further reduced.

The second high concentration region 202 may be formed to a positiondeeper than the lower end of the guard ring 92. As a result, the secondhigh concentration region 202 and the high concentration region 460 canbe easily connected. In another example, the second high concentrationregion 202 may be formed up to a position shallower than the lower endof the guard ring 92. The first peak 401 of the this example is arrangedin the second high concentration region 202. The first peak 401 may beprovided at a position in contact with the guard ring 92. As a result,the high concentration region 460 can be formed up to the proximity ofthe upper surface 21, and the second high concentration region 202 andthe high concentration region 460 can be easily connected.

In the edge termination structure portion 90, the bulk doping region 18having the bulk donor concentration may remain or the second highconcentration region 202 may be provided without the bulk doping region18 remaining, further outside the outermost guard ring 92. In the thisexample, the bulk doping region does not remain. In the example of FIG.14, the second high concentration region 202 does not cover a part ofthe lower end of the guard ring 92. As indicated by a broken line inFIG. 14, the second high concentration region 202 may cover entire guardring 92.

FIG. 15 illustrates a diagram showing another example of the crosssection c-c in FIG. 8. In the semiconductor device 100 of the thisexample, the arrangement of the high concentration regions 460 in atleast a part of the region 91 of the edge termination structure portion90 is different from that of the example illustrated in FIG. 11, FIG.13A, FIG. 13B, FIG. 13C, or FIG. 14. In the region 91, a third highconcentration region 203 may be provided instead of the second highconcentration region 202. The third high concentration region 203 is ahigh concentration region formed to a position deeper than the secondhigh concentration region 202. One or more of the bulk doping region 18,the second high concentration region 202, the high concentration region460, and the third high concentration region 203 may be provided in theregion 91. Other structures are the same as the example illustrated inFIG. 11, FIG. 13A, FIG. 13B, FIG. 13C, or FIG. 14.

The high concentration region 460 in FIG. 15 is not provided in theregion 91 having a predetermined width in contact with the end side 102of the semiconductor substrate 10 in the edge termination structureportion 90. The region 91 may include one or more guard rings 92. Theregion 91 may be provided with the bulk doping region 18 of the bulkdonor concentration instead of the high concentration region 460. Thehigh concentration region 460 may not be formed in the edge terminationstructure portion 90. The outer circumferential end of the highconcentration region 460 may be located on the inner peripheral side ofthe guard ring 92 located on the innermost periphery. In anotherexample, the high concentration region 460 may also be provided in theregion 91. The high concentration region 460 in the region 91 may havethe same, shorter, or longer length in the Z axis direction than thehigh concentration region 460 arranged inside the region 91.

The edge termination structure portion 90 inside the region 91 has thesame structure as the example illustrated in FIG. 11, FIG. 13A, FIG.13B, FIG. 13C, or FIG. 14. The edge termination structure portion 90inside the region 91 includes one or more guard rings 92. As illustratedin FIG. 11, FIG. 13A, FIG. 13B, FIG. 13C, or FIG. 14, the highconcentration region 460 may be provided in a range including the lowerend of guard ring 92, or may be provided in a range not including thelower end of the guard ring 92.

The second high concentration region 202 may or may not be provided inthe region 91. Alternatively, instead of the second high concentrationregion 202, an N type third high concentration region 203 having a donorconcentration higher than the bulk donor concentration may be provided.The donor concentration in the third high concentration region 203 maybe the same as or different from the donor concentration in the secondhigh concentration region 202. The third high concentration region 203is provided from the upper surface 21 of the semiconductor substrate 10to a position deeper than the lower end of the second high concentrationregion 202. The third high concentration region 203 of the this examplemay be provided up to a position deeper than the lower end of the guardring 92. The bulk doping region 18 is provided between the third highconcentration region 203 and the buffer region 20.

The third high concentration region 203 may be formed by implanting adonor such as phosphorous or hydrogen from the upper surface 21. Theimplantation depth of the donor in the third high concentration region203 may be deeper than the implantation depth of the donor in the secondhigh concentration region 202. The heat treatment for the second highconcentration region 202 and the third high concentration region 203 maybe performed individually or in common.

FIG. 16 illustrates a diagram showing another example of the crosssection c-c in FIG. 8. The semiconductor device 100 of the this exampleis different from the semiconductor device 100 described in FIG. 1 toFIG. 15 in the range in the XY plane in which the high concentrationregion 460 is provided. The range in the XY plane in which the firstpeak 401 is provided may also be different from the example described inFIG. 1 to FIG. 15. The structure other than the high concentrationregion 460 and the first peak 401 may be the same as any aspectdescribed in FIG. 1 to FIG. 15. In FIG. 16, the arrangement of the highconcentration region 460 and the first peak 401 is different from thatof the example illustrated in FIG. 11. In addition, in the exampleillustrated in FIG. 16, the second high concentration region 202 is notprovided as compared with the example illustrated in FIG. 11. Otherstructures are the same as those in the example illustrated in FIG. 11.

The high concentration region 460 of the this example is at leastpartially provided in the edge termination structure portion 90 and isprovided in a range not reaching the active portion 160. The highconcentration region 460 may be provided only in the edge terminationstructure portion 90, or may be provided from the edge terminationstructure portion 90 to below the well region 11. In the example of FIG.16, the high concentration region 460 is provided from the end portionof the semiconductor substrate 10 in the X axis direction to below thewell region 11.

In the this example, since the high concentration region 460 is notprovided in the active portion 160, characteristic variation of theactive portion 160 due to the provision of the high concentration region460 can be prevented. Since the high concentration region 460 isprovided in the edge termination structure portion 90, the expanding ofthe depletion layer in the edge termination structure portion 90 can besuppressed, and the area of the edge termination structure portion 90 inthe XY plane can be reduced.

FIG. 17 illustrates a diagram showing another example of the crosssection c-c in FIG. 8. The semiconductor device 100 of the this exampleis different from the example described in FIG. 16 in that the secondhigh concentration region 202 is provided. Other structures are the sameas those of the semiconductor device 100 of any aspect described in FIG.16. Also in the this example, it is possible to suppress the expandingof the depletion layer in the edge termination structure portion 90while preventing the characteristic variation of the active portion 160.

FIG. 18A illustrates a diagram showing another example of the crosssection c-c in FIG. 8. In the semiconductor device 100 of the thisexample, the upper end position of the high concentration region 460 inthe Z axis direction and the position of the first peak 401 in the Zaxis direction are different from those in the example described withreference to FIG. 16 or FIG. 17. Other structures are the same as any ofthe examples described in FIG. 16 or FIG. 17. In the example illustratedin FIG. 18A, as in the example of FIG. 17, the second high concentrationregion 202 is provided. The upper end position of the high concentrationregion 460 in the Z axis direction and the position of the first peak401 in the Z axis direction are the same as those in the exampledescribed in FIG. 13A. Also in the this example, it is possible tosuppress the expanding of the depletion layer in the edge terminationstructure portion 90 while preventing the characteristic variation ofthe active portion 160.

FIG. 18B illustrates a diagram showing another example of the crosssection c-c in FIG. 8. The semiconductor device 100 of the this exampleis different from the example illustrated in FIG. 18A in the range inthe depth direction in which the high concentration region 460 isprovided. The position of the first peak 401 in the depth direction mayalso be different from the example illustrated in FIG. 18A. Otherstructures may be the same as the example illustrated in FIG. 18A.

In the this example, the range in which the high concentration region460 is provided and the depth position in which the first peak 401 isprovided are similar to those in the example of FIG. 13B. That is, thefirst peak 401 of the this example is arranged at a depth positionoverlapping the channel stopper 174. Similarly, the peak of the hydrogenchemical concentration is arranged at a position overlapping the channelstopper 174. The high concentration region 460 of the this example isprovided up to a depth position overlapping the channel stopper 174.

In a region below the channel stopper 174 of the this example, the highconcentration region 460 is provided, and the bulk doping region 18 doesnot remain. Therefore, it is possible to suppress the depletion layerexpanding in the X axis direction from extending to the outside of thechannel stopper 174.

FIG. 18C illustrates a diagram showing another example of the crosssection c-c in FIG. 8. The semiconductor device 100 of the this exampleis different from the example illustrated in FIG. 18A or FIG. 18B in therange in the depth direction in which the high concentration region 460is provided. In addition, the first peak 401 does not exist in thesemiconductor substrate 10. Other structures may be the same as theexamples illustrated in FIG. 18A or FIG. 18B.

In the this example, as in the example of FIG. 13C, impurities(hydrogen) are implanted from the lower surface 23 of the semiconductorsubstrate 10 so as to penetrate the semiconductor substrate 10. In thethis example, the depth range in which the high concentration region 460is provided is similar to that in the example of FIG. 13 C. That is, thehigh concentration region 460 is formed from the lower surface 23 to theupper surface 21 of the semiconductor substrate 10.

In a region below the channel stopper 174 of the this example, the highconcentration region 460 is provided, and the bulk doping region 18 doesnot remain. Therefore, it is possible to suppress the depletion layerexpanding in the X axis direction from extending to the outside of thechannel stopper 174. In addition, since the first peak 401 does notexist, the influence on the doping region (for example, the well region11 and the guard ring 92) locally provided on the upper surface 21 sideof the semiconductor substrate 10 can be reduced.

FIG. 19 illustrates a diagram showing another example of the crosssection c-c in FIG. 8. The semiconductor device 100 of the this exampleis different from the example illustrated in FIG. 18A, FIG. 18B, or FIG.18C in the structure of the second high concentration region 202. Otherstructures are the same as the examples illustrated in FIG. 18 A, FIG.18B, or FIG. 18C. The second high concentration region 202 of the thisexample has the same structure as the example illustrated in FIG. 14.Also in the this example, it is possible to suppress the expanding ofthe depletion layer in the edge termination structure portion 90 whilepreventing the characteristic variation of the active portion 160.

FIG. 20 illustrates a diagram showing another example of the crosssection c-c in FIG. 8. The semiconductor device 100 of the this exampleis different from the semiconductor device 100 described in FIG. 16 toFIG. 19 in that the high concentration region 460 has a plurality ofregions having different lengths in the Z axis direction. The positionof the first peak 401 in the Z axis direction is also different in eachregion of the high concentration region 460. Other structures are thesame as any of the examples described in FIG. 16 to FIG. 19.

The high concentration region 460 has an inner portion and an outerportion provided outside the inner portion. The outside refers to a sidefar from the active portion 160 in the XY plane. The outer portion has alarger length in the Z axis direction than the inner portion. In theexample of FIG. 20, the high concentration region 460 includes a highconcentration region 460-1, a high concentration region 460-2, and ahigh concentration region 460-3. The high concentration region 460-2 isarranged outside the high concentration region 460-1 and is providedlonger than the high concentration region 460-1 in the Z axis direction.The high concentration region 460-3 is arranged outside the highconcentration region 460-2 and is provided longer than the highconcentration region 460-2 in the Z axis direction. That is, if the highconcentration region 460-1 is an inner portion, the high concentrationregion 460-2 and the high concentration region 460-3 are outer portions.If the high concentration region 460-2 is an inner portion, the highconcentration region 460-3 is an outer portion. In the this example, thelength of each region of the high concentration region 460 in the Z axisdirection varies stepwise.

An upper end of each high concentration region 460 may be arranged inthe drift region 19. In another example, the upper end of the highconcentration region 460-3 may be arranged at a position overlapping theguard ring 92 or the well region 11.

A first peak 401-2 included in the high concentration region 460-2 isprovided at a position above a first peak 401-1 included in the highconcentration region 460-1 in the Z axis direction. A first peak 401-3included in the high concentration region 460-3 is provided at aposition above the first peak 401-2 included in the high concentrationregion 460-2 in the Z axis direction.

According to the semiconductor device 100 of the this example, since thehigh concentration region 460 in the vicinity of the active portion 160is short in the Z axis direction, the influence of the highconcentration region 460 on the characteristics of the active portion160 can be suppressed. In addition, since the high concentration region460 away from the active portion 160 is long in the Z axis direction,the expanding of the depletion layer in the edge termination structureportion 90 can be suppressed.

FIG. 21A illustrates a diagram showing another example of the crosssection c-c in FIG. 8. The semiconductor device 100 of the this exampleis different from the semiconductor device 100 described in FIG. 16 toFIG. 19 in that the high concentration region 460 has a plurality ofregions having different lengths in the Z axis direction. The positionof the first peak 401 in the Z axis direction is also different in eachregion of the high concentration region 460. Other structures are thesame as any of the examples described in FIG. 16 to FIG. 19.

The high concentration region 460 of the this example is different fromthe high concentration region 460 of FIG. 20 in that the length in the Zaxis direction gradually increases as the distance from the activeportion 160 increases. Other structures may be the same as in theexample of FIG. 20. The first peak 401 of the this example is arrangedon the upper side as it goes away from the active portion 160. Also inthe this example, the entire upper end of the high concentration region460 may be arranged in the drift region 19. In other examples, a portionof the upper end of the high concentration region 460 may be arranged ata position overlapping the guard ring 92 or the well region 11. Also inthe this example, the influence of the high concentration region 460 onthe characteristics of the active portion 160 can be suppressed.Further, the expanding of the depletion layer in the edge terminationstructure portion 90 can be suppressed.

FIG. 21B illustrates a diagram showing another example of the crosssection c-c in FIG. 8. In the semiconductor device 100 of the thisexample, the depth range in which the high concentration region 460 isprovided and the position of the first peak 401 are different from thosein the example of FIG. 21A. Other structures are the same as the exampleof FIG. 21A.

As in the example of FIG. 21A, the depth position of the first peak 401is closer to the upper surface 21 with increasing distance from theactive portion 160. Similarly, the depth position of the peak of thehydrogen chemical concentration is closer to the upper surface 21 withincreasing distance from the active portion 160. A peak of the hydrogenchemical concentration may be provided at the position of the first peak401. In the this example, the first peak 401 overlaps the channelstopper 174. The first peak 401 may also overlap one or more guard rings92. In addition, in a region close to the side wall of the semiconductorsubstrate 10, hydrogen ions implanted from the lower surface 23 maypenetrate the semiconductor substrate 10. The first peak 401 is notprovided in the region through which the hydrogen ions penetrate. Forexample, in the channel stopper 174, the first peak 401 may not beprovided in a region in contact with the side wall of the semiconductorsubstrate 10.

Also in the high concentration region 460, the length in the Z axisdirection gradually increases as the high concentration region is awayfrom the active portion 160. The high concentration region 460 of thethis example is formed from the lower surface 23 to a position incontact with or overlapping the channel stopper 174. In a region belowthe channel stopper 174 of the this example, the high concentrationregion 460 is provided, and the bulk doping region 18 does not remain.Therefore, it is possible to suppress the depletion layer expanding inthe X axis direction from extending to the outside of the channelstopper 174.

FIG. 22 illustrates a diagram showing an example of a method for formingthe high concentration region 460 described in FIG. 20. In the thisexample, hydrogen ions are radiated from the lower surface 23 side whilethe shielding member 350 is arranged below the lower surface 23 of thesemiconductor substrate 10. The shielding member 350 covers the entireactive portion 160 and at least a part of the edge termination structureportion 90. The shielding member 350 covering the active portion 160 hasa thickness that completely shields hydrogen ions and does not reach thesemiconductor substrate 10.

The shielding member 350 covering the region where the highconcentration region 460 is to be provided has a thickness correspondingto the length in the Z axis direction of each high concentration region460. That is, the shielding member 350 is thinner in the region wherethe high concentration region 460 is formed longer. By thinning theshielding member 350, hydrogen ions reach deep in the semiconductorsubstrate 10, and the high concentration region 460 becomes long.

In the shielding member 350 of the this example, the shielding member350 becomes thinner stepwise as the distance from the active portion 160increases. The shielding member 350 may or may not be provided below thehigh concentration region 460-3. In FIG. 22, the collector electrode 24is provided, but the lower surface 23 may be radiated with hydrogen ionsbefore the collector electrode 24 is formed.

FIG. 23 illustrates a diagram showing an example of a method for formingthe high concentration region 460 described in FIG. 21A. In the thisexample, the shape of the shielding member 350 is different from that ofthe example of FIG. 22. Other conditions are the same as those in theexample of FIG. 22.

In the shielding member 350 of the this example, the shielding member350 becomes thinner linearly or curvilinearly as it goes away from theactive portion 160. The shielding member 350 may or may not be providedbelow the high concentration region 460-3.

In the forms illustrated in FIG. 16 to FIG. 23, the specific resistance(resistivity) of the high concentration region 460 is lower than thespecific resistance of the drift region 19 in the active portion 160(the transistor portion 70 or the diode portion 80). The specificresistance of the high concentration region 460 may be 1/1.5 or less and1/10 or more of the specific resistance of the drift region 19 of theactive portion 160. The specific resistance of the high concentrationregion 460 may be 1/2 or less of the specific resistance of the driftregion 19 of the active portion 160. As the specific resistance of eachregion, a central value in the Z axis direction of each region may beused, or an average value may be used.

In the forms illustrated in FIG. 16 to FIG. 23, the specific resistanceof the drift region 19 of the active portion 160 may have a valueaccording to the rated voltage of the semiconductor device 100. As anexample, the specific resistance may be 20 to 80 Ωcm in a case where therated voltage is 600 V, the specific resistance may be 40 to 120 Ωcm ina case where the rated voltage is 1200 V, the specific resistance may be60 to 200 Ωcm in a case where the rated voltage is 1700 V, and thespecific resistance may be 150 to 450 Ωcm in a case where the ratedvoltage is 3300 V.

In the forms illustrated in FIG. 1 to FIG. 23, the semiconductorsubstrate 10 may have bulk acceptors of the second conductivity typedistributed throughout. The bulk acceptors, like bulk donors, areacceptors that are uniformly introduced into ingots during ingotmanufacture. The bulk acceptors may be boron. The bulk acceptorconcentration may be lower than the bulk donor concentration. That is,the ingot is an N type ingot. As an example, the bulk acceptorconcentration is between 5×10¹¹ (/cm³) and 9×10¹³ (/cm³), and the bulkdonor concentration is between 5×10¹² (/cm³) and 1×10¹⁴ (/cm³). The bulkacceptor concentration may be 1% or more, 10% or more, or 50% or more ofthe bulk donor concentration. The bulk acceptor concentration may be 99%or less, 95% or less, or 90% or less of the bulk donor concentration.

The existence of the bulk acceptor in the entire semiconductor substrate10 makes it possible to reduce the net doping concentration in thesemiconductor substrate 10 before hydrogen ions and the like areimplanted. Therefore, the absolute value of the variation in the netdoping concentration of the semiconductor substrate 10 can be reduced.Therefore, the specific resistance can be easily adjusted by theimplantation of hydrogen ions.

The oxygen annealing described in FIG. 1 to FIG. 7 may be performedbefore the structures other than the bulk doping region 18 are formedamong the structures described in FIG. 8 to FIG. 23. In another example,the oxygen annealing may be performed after forming each doping regioninside the semiconductor substrate 10. In this case, the films such asthe interlayer dielectric film 38 and the gate dielectric film 42 eachmay be formed after the oxygen annealing. Accordingly, deterioration ofcharacteristics of the dielectric film and the like due to oxygenannealing can be suppressed.

Before oxygen annealing is performed, an N type dopant such asphosphorous may be implanted into the upper surface of the semiconductorsubstrate 10. The N type dopant may be selectively implanted in a topview or may be implanted over the entire surface. The N type dopant maybe implanted in a region where the third high concentration region 203is formed. After the N type dopant is implanted, the semiconductorsubstrate 10 is annealed at 1100° C. or more and 1300° C. or less for 20hours or more in an oxygen atmosphere (first annealing). As a result,the N type dopant can be diffused to a relatively deep depth. The N typedopant may be diffused until it reaches the high concentration region460. Thus, the donor concentration of the semiconductor substrate 10 canbe adjusted over the entire depth direction. Note that oxygen having aconcentration equal to the solid solubility limit is introduced into thesemiconductor substrate 10 by the first annealing.

Next, the semiconductor substrate 10 is annealed at a temperature lowerthan that of the first annealing (second annealing). The secondannealing may be performed in an oxygen atmosphere. The annealing timeof the second annealing may be shorter than that of the first annealing.For example, the first annealing is performed at 900° C. or more and1000° C. or less for 15 hours or less. As a result, oxygen in thesemiconductor substrate 10 diffuses outward, and the upper surface sideoxygen reduction region 450 is formed. After the second annealing, thestructures other than the third high concentration region 203 may beformed. The second annealing may be included in the step of forming thestructure on the upper surface 21 side of the semiconductor substrate10.

Note that the temperature of the first annealing may be 1000° C. orlower. In this case, it is possible to suppress oxygen from beingintroduced into the semiconductor substrate 10 in the first annealing.

While the description has been made using the embodiments of the presentinvention, the technical scope of the present invention is not limitedto the above described embodiments. It is apparent to persons skilled inthe art that various alterations and improvements can be added to theabove-described embodiments. It is also apparent from the scope of theclaims that the embodiments added with such alterations or improvementscan be included in the technical scope of the present invention.

It should be noted that the operations, procedures, steps, and stages ofeach process performed by an apparatus, system, program, and methodshown in the claims, specification, or drawings can be performed in anyorder as long as the order is not indicated by “prior to,” “before,” orthe like and as long as the output from a previous process is not usedin a later process. Even if the operation flow is described usingphrases such as “first” or “next” in the claims, specification, ordrawings, it does not necessarily mean that the process must beperformed in this order.

EXPLANATION OF REFERENCES

-   -   10: semiconductor substrate    -   11: well region    -   12: emitter region    -   14: base region    -   15: contact region    -   16: accumulation region    -   18: bulk doping region    -   19: drift region    -   20: buffer region    -   21: upper surface    -   22: collector region    -   23: lower surface    -   24: collector electrode    -   29: linear portion    -   30: dummy trench portion    -   31: edge portion    -   32: dummy dielectric film    -   34: dummy conductive portion    -   38: interlayer dielectric film    -   39: linear portion    -   40: gate trench portion    -   41: edge portion    -   42: gate dielectric film    -   44: gate conductive portion    -   52: emitter electrode    -   54: contact hole    -   60, 61: mesa portion    -   70: transistor portion    -   80: diode portion    -   81: extension region    -   82: cathode region    -   90: edge termination structure portion    -   91: region    -   92: guard ring    -   94: field plate    -   100: semiconductor device    -   102: end side    -   106: pass-through region    -   112: gate pad    -   130: outer circumferential gate runner    -   131: active-side gate runner    -   160: active portion    -   174: channel stopper    -   202: second high concentration region    -   203: third high concentration region    -   313: flat portion    -   314: peak    -   318: phosphorous concentration peak    -   323: flat portion    -   350: shielding member    -   401: first peak    -   402: second peak    -   403: third peak    -   404: fourth peak    -   405: oxygen concentration peak    -   406: recombination center peak    -   407: donor concentration peak    -   408: peak    -   411, 412, 413, 414: upper tail    -   421, 422, 423, 424: lower tail    -   425: fifth peak    -   426: sixth peak    -   435, 436: upper tail    -   445, 446: lower tail    -   450: upper surface side oxygen reduction region    -   452: maximum value region    -   454: lower surface side oxygen reduction region    -   460: high concentration region

What is claimed is:
 1. A semiconductor device comprising: asemiconductor substrate that has an upper surface and a lower surfaceand throughout which a bulk donor of a first conductivity type isdistributed; a high concentration region of a first conductivity typethat includes a center position in a depth direction of thesemiconductor substrate and has a donor concentration higher than adoping concentration of the bulk donors; and an upper surface sideoxygen reduction region that is provided in contact with the uppersurface of the semiconductor substrate inside the semiconductorsubstrate and in which an oxygen chemical concentration decreases asapproaching the upper surface of the semiconductor substrate.
 2. Thesemiconductor device according to claim 1, wherein a first peak at whicha distribution of an impurity chemical concentration becomes a peak isarranged in an end portion in the depth direction of the highconcentration region.
 3. The semiconductor device according to claim 2,wherein an oxygen chemical concentration distribution in the depthdirection of the semiconductor substrate includes a position where theoxygen chemical concentration becomes a maximum value and has a maximumvalue region where the oxygen chemical concentration is 50% or more ofthe maximum value, and the first peak is arranged in the maximum valueregion or on the upper surface side of the semiconductor substrate withrespect to the maximum value region.
 4. The semiconductor deviceaccording to claim 2, wherein the distribution of the impurity chemicalconcentration in the depth direction includes a lower tail extendingfrom the first peak toward the lower surface, and an upper tail in whichthe impurity chemical concentration more steeply decreases than thelower tail from the first peak toward the upper surface.
 5. Thesemiconductor device according to claim 2, wherein the highconcentration region is provided from the first peak to the lowersurface of the semiconductor substrate.
 6. The semiconductor deviceaccording to claim 3, wherein the oxygen chemical concentrationdistribution has an oxygen concentration peak at which the oxygenchemical concentration exhibits a local maximum value.
 7. Thesemiconductor device according to claim 2, comprising a second peak of ahydrogen chemical concentration, arranged between the first peak and thelower surface.
 8. The semiconductor device according to claim 7, furthercomprising a lower surface side oxygen reduction region that is arrangedon the lower surface side with respect to the upper surface side oxygenreduction region and in which an oxygen chemical concentration decreasesas approaching the lower surface of the semiconductor substrate, whereinthe second peak of the hydrogen chemical concentration is arranged inthe lower surface side oxygen reduction region.
 9. The semiconductordevice according to claim 7, wherein the second peak of the hydrogenchemical concentration is arranged in the maximum value region.
 10. Thesemiconductor device according to claim 7, further comprising: a driftregion of a first conductivity type provided in the semiconductorsubstrate; and a buffer region that is arranged between the drift regionand the lower surface and has a higher doping concentration than thedrift region, wherein the second peak of the hydrogen chemicalconcentration is arranged in the buffer region.
 11. The semiconductordevice according to claim 1, wherein a recombination centerconcentration distribution in the depth direction of the semiconductorsubstrate has a recombination concentration peak, and the recombinationconcentration peak is arranged in a region where the oxygen chemicalconcentration is 70% or more of the maximum value.
 12. The semiconductordevice according to claim 2, wherein the first peak is arranged in aregion where the oxygen chemical concentration is 70% or more of themaximum value.
 13. The semiconductor device according to claim 2,wherein the impurity chemical concentration is a hydrogen chemicalconcentration.
 14. The semiconductor device according to claim 1,wherein the bulk donor is phosphorous or antimony.
 15. The semiconductordevice according to claim 1, wherein a bulk acceptor of a secondconductivity type is distributed throughout the semiconductor substrate.16. The semiconductor device according to claim 15, wherein the bulkacceptor is boron.
 17. The semiconductor device according to claim 1,further comprising: one or more guard rings that are in contact with anupper surface of the semiconductor substrate and have a secondconductivity type; and a channel stopper of a first conductivity type ora second conductivity type which is provided further outside anoutermost guard ring, is in contact with the upper surface of thesemiconductor substrate, and have a doping concentration higher thanthat of the bulk donor, wherein the channel stopper contains hydrogen.18. The semiconductor device according to claim 17, wherein hydrogen isdistributed from a lower surface of the semiconductor substrate to thechannel stopper.
 19. The semiconductor device according to claim 17,wherein a peak of a hydrogen chemical concentration is provided in thechannel stopper.
 20. The semiconductor device according to claim 1,wherein the high concentration region is provided up to the lowersurface of the semiconductor substrate.
 21. The semiconductor deviceaccording to claim 20, wherein the high concentration region is providedup to a position not in contact with the upper surface of thesemiconductor substrate.
 22. The semiconductor device according to claim20, wherein the high concentration region is provided up to a positionoverlapping the upper surface side oxygen reduction region.
 23. Thesemiconductor device according to claim 20, wherein the highconcentration region is provided up to the upper surface of thesemiconductor substrate.
 24. The semiconductor device according to claim1, wherein an oxygen chemical concentration distribution in the depthdirection of the semiconductor substrate includes a position where theoxygen chemical concentration becomes a maximum value and has a maximumvalue region where the oxygen chemical concentration is 50% or more ofthe maximum value, and the maximum value region and the highconcentration region are provided to be overlapped in a partial regionin a depth direction of the semiconductor substrate.
 25. Thesemiconductor device according to claim 1, wherein an emitter region ofa first conductivity type is arranged in the upper surface of thesemiconductor substrate.